UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549

                                    FORM 10-K

(Mark One)
|X| ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT
OF 1934 For the fiscal year ended: December 31, 2006
                                       or

|_| TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE
ACT OF 1934

For Transition period ______________________________


             Commission File Number of issuing entity: 333-131201-05
                           RFMSI SERIES 2006-SA2 TRUST
           (Exact name of issuing entity as specified in its charter)

                 RESIDENTIAL FUNDING MORTGAGE SECURITIES I, INC.
              (Exact name of depositor as specified in its charter)

                        RESIDENTIAL FUNDING COMPANY, LLC
               (Exact name of sponsor as specified in its charter)

                                    New York
                 ------------------------------------ ---------
 (State or other jurisdiction of incorporation or organization of the issuing
entity)

            c/o Residential Funding Company, LLC, as Master Servicer
                         8400 Normandale Lake Boulevard
                          Minneapolis, Minnesota 55437
--------------------------------------------------------------------------------

           (Address of principal executive offices of issuing entity)

             (952) 857-7000 (Telephone number, including area code)

                                      None
                      (I.R.S. Employer Identification No.)

                                       N/A
                              --------------- ----
           (Former name, former address, if changed since last report)

Securities registered pursuant to Section 12(b) of the Act: None
Securities Registered pursuant to Section 12(g) of the Act: None
Indicate by check mark if the  registrant is a well-known  seasoned  issuer,  as
defined in Rule 405 of the Securities Act.
Yes |_|  No  |X|
Indicate  by  check  mark if the  registrant  is not  required  to file  reports
pursuant to Section 13 or Section 15(d) of the Act.

<PAGE>

Yes |X|  No  |_|
Indicate by check mark whether the registrant (1) has filed all reports required
to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during
the  preceding 12 months (or for such  shorter  period that the  registrant  was
required  to file  such  reports),  and  (2) has  been  subject  to such  filing
requirements  for the past 90 days.  |X| Yes |_| No  Indicate  by check  mark if
disclosure of delinquent  filers  pursuant to Item 405 of Regulation  S-K is not
contained  herein,  and  will  not be  contained,  to the  best of  registrant's
knowledge,  in  definitive  proxy  or  information  statements  incorporated  by
reference in Part II of the Form 10-K or any amendment to this Form 10-K. |X|
[Item 405 of Regulation S-K is not applicable.]
Indicate by check mark whether the registrant is a large  accelerated  filer, an
accelerated  filer, or a  non-accelerated  filer. See definition of "accelerated
filer and large  accelerated  filer" in Rule 12b-2 of the Exchange  Act.  (Check
one): Large accelerated filer |_| Accelerated  filer |_|  Non-accelerated  filer
|X| Indicate by check mark whether the registrant is a shell company (as defined
in Rule 12b-2 of the Act). Yes |_| No |X| Registrant has no voting or non-voting
common equity outstanding held by non-affiliates.


<PAGE>


                                     PART I

THE FOLLOWING ITEMS HAVE BEEN OMITTED IN ACCORDANCE  WITH GENERAL  INSTRUCTION J
TO FORM 10-K:

Item 1: Business.
Item 1A: Risk Factors.
Item 2: Properties.
Item 3: Legal Proceedings.
Item 4: Submission of Matters to a Vote of Security Holders.

ITEM 1B. UNRESOLVED STAFF COMMENTS.

Not Applicable.

SUBSTITUTE INFORMATION PROVIDED IN ACCORDANCE WITH GENERAL INSTRUCTION J TO FORM
10-K:

ITEM 1112(B) OF REGULATION AB.  SIGNIFICANT  OBLIGORS OF POOL ASSETS  (FINANCIAL
INFORMATION).

None.

ITEM 1114(B)(2) OF REGULATION AB: CREDIT  ENHANCEMENT AND OTHER SUPPORT,  EXCEPT
FOR CERTAIN DERIVATIVES INSTRUMENTS (FINANCIAL INFORMATION).

None.

ITEM  1115(B) OF  REGULATION  AB:  CERTAIN  DERIVATIVES  INSTRUMENTS  (FINANCIAL
INFORMATION).

Based  on the  standards  set  forth  in  Item  1115(b)  of  Regulation  AB,  no
information is required in response to this Item.

ITEM 1117 OF REGULATION AB: LEGAL PROCEEDINGS.

There are no material pending legal or other proceedings  involving the mortgage
loans or Residential Funding Company,  LLC ("Residential  Funding"),  as sponsor
and master  servicer,  Residential  Funding  Mortgage  Securities  I,  Inc.,  as
depositor,  RFMSI Series  2006-SA2  Trust,  as the issuing  entity,  Homecomings
Financial,   LLC   ("Homecomings")   and  GMAC  Mortgage,   LLC  ("GMACM"),   as
subservicers,  or other  parties  described in Item 1117 of  Regulation AB that,
individually  or in the  aggregate,  would  have a  material  adverse  impact on
investors in the securities (the "Securities") to which this report relates.


<PAGE>

Residential  Funding,  Homecomings  and GMACM are  currently  parties to various
legal  proceedings  arising  from time to time in the  ordinary  course of their
businesses,  some of which  purport to be class  actions.  Based on  information
currently available,  it is the opinion of Residential Funding,  Homecomings and
GMACM that the  eventual  outcome of any  currently  pending  legal  proceeding,
individually  or in the  aggregate,  will not have a material  adverse effect on
their ability to perform their obligations in relation to the mortgage loans. No
assurance,  however,  can be  given  that  the  final  outcome  of  these  legal
proceedings, if unfavorable,  either individually or in the aggregate, would not
have a material adverse impact on Residential Funding, Homecomings or GMACM. Any
such  unfavorable  outcome  could  adversely  affect the ability of  Residential
Funding,  Homecomings  or GMACM to perform its servicing  duties with respect to
the  mortgage  loans and  potentially  lead to the  replacement  of  Residential
Funding, Homecomings or GMACM with a successor servicer.


                                     PART II

THE FOLLOWING ITEMS HAVE BEEN OMITTED IN ACCORDANCE  WITH GENERAL  INSTRUCTION J
TO FORM 10-K:

Item 5: Market for Registrant's  Common Equity,  Related Stockholder Matters and
     Issuer Purchases of Equity Securities.

Item 6:    Selected Financial Data.

Item 7: Management's  Discussion and Analysis of Financial Condition and Results
     of Operations.

Item 7A:   Quantitative and Qualitative Disclosures about Market Risk.
Item 8:    Financial Statements and Supplementary Data.

Item 9:  Changes  in  and  Disagreements  with  Accountants  on  Accounting  and
     Financial Disclosure. Item 9A: Controls and Procedures.

ITEM 9B: OTHER INFORMATION.

None.

                                    PART III

THE FOLLOWING ITEMS HAVE BEEN OMITTED IN ACCORDANCE  WITH GENERAL  INSTRUCTION J
TO FORM 10-K:

Item 10:   Directors and Executive Officers of the Registrant.
Item 11:   Executive Compensation.

Item 12:  Security  Ownership of Certain  Beneficial  Owners and  Management and
     Related Stockholder Matters.

Item 13:   Certain Relationships and Related Transactions.
Item 14:   Principal Accountant Fees and Services.


<PAGE>

SUBSTITUTE INFORMATION PROVIDED IN ACCORDANCE WITH GENERAL INSTRUCTION J TO FORM
10-K:

ITEM 1119 OF REGULATION AB:  AFFILIATIONS AND CERTAIN RELATIONSHIPS AND RELATED
TRANSACTIONS.

Information  contemplated  by Item 1119 of  Regulation  AB has been omitted from
this report in reliance on the Instruction to Item 1119.

ITEM 1122 OF REGULATION AB: COMPLIANCE WITH APPLICABLE SERVICING CRITERIA.

Each of  Residential  Funding  Company,  LLC, GMAC  Mortgage,  LLC,  Homecomings
Financial,  LLC, U.S. Bank National  Association and Wells Fargo Bank,  National
Association  (each,  a  "Servicing  Participant")  has  been  identified  by the
registrant as a party  participating  in the servicing  function with respect to
the pool assets held by the  Issuing  Entity.  Each  Servicing  Participant  has
completed a report on an assessment of  compliance  with the servicing  criteria
applicable to such Servicing  Participant (each, a "Report on Assessment") as of
December 31, 2006 and for the period covered by this Form 10-K, which Reports on
Assessment  are  attached  as  exhibits  to this Form 10-K.  In  addition,  each
Servicing  Participant has provided an attestation report (each, an "Attestation
Report") by a  registered  independent  public  accounting  firm  regarding  its
related Report on Assessment.  Each Attestation Report is attached as an exhibit
to this Form 10-K.

A Servicing  Participant may engage one or more vendors to perform  specific and
limited,  or scripted  activities  that  address all or a portion of one or more
servicing criteria applicable to such Servicing Participant. In these cases, the
Servicing  Participant has instituted policies and procedures to monitor whether
such vendors'  activities  comply in all material  respects with such  servicing
criteria, and may elect to take responsibility for assessing compliance with the
servicing  criteria  applicable  to such vendors'  activities in such  Servicing
Participant's Report on Assessment.

Except as disclosed below, no Report on Assessment or related Attestation Report
has identified  (i) any material  instance of  noncompliance  with the servicing
criteria  identified  in such Report on  Assessment as applicable to the related
Servicing  Participant  or  (ii)  any  material  deficiency  in  such  Servicing
Participant's policies and procedures to monitor vendor compliance.

Exceptions:

Residential  Funding  Company,   LLC:  The  Report  on  Assessment  prepared  by
Residential  Funding  Company,  LLC  and the  related  Attestation  Report  have
identified material noncompliance with one servicing criterion applicable to it.
Specifically,   with  regard  to  servicing  criterion  1122(d)(3)(i)(B)  (which
contemplates  that  reports  to  investors  provide  information  calculated  in
accordance with the terms specified in the transaction agreements),  information
required  by the  transaction  agreements  was  excluded  from,  or  incorrectly
reported in, certain of the investor  reports.  The registrant  does not believe
these  reporting  errors had any material  impacts or effects on  investors  and
corrective action was completed to address ongoing compliance.


<PAGE>

Platform-Level Reports:

Regulations of the Securities and Exchange  Commission  (the "SEC") require that
each  Servicing  Participant  complete a Report on  Assessment  at a  "platform"
level,  meaning that the transactions covered by the Report on Assessment should
include  all  asset-backed  securities  transactions  involving  such  Servicing
Participant  that are backed by the same asset type.  More recent  guidance from
the SEC staff identifies additional parameters which a Servicing Participant may
apply to define  and  further  limit its  platform.  For  example,  a  Servicing
Participant  may define its  platform  to include  only  transactions  that were
completed  on or after  January  1, 2006 and that were  registered  with the SEC
pursuant  to  the  Securities  Act  of  1933.  Each  Servicing   Participant  is
responsible  for defining its own platform,  and each  platform  will  naturally
differ based on various factors,  including the Servicing Participant's business
model and the transactions in which it is involved.

Based on our understanding of their platforms and the guidance that is available
at this time, we believe that the parameters by which the Servicing Participants
have defined their platforms should be permissible.  However,  because the SEC's
regulations  are new and the guidance  that is available at this time is subject
to clarification or change, we cannot assure you that the SEC and its staff will
necessarily agree.

ITEM 1123 OF REGULATION AB: SERVICER COMPLIANCE STATEMENT.

Each of Residential  Funding  Company,  LLC, GMAC Mortgage,  LLC and Homecomings
Financial,  LLC (each, a "Servicer")  has been identified by the registrant as a
servicer  with  respect to the pool  assets  held by the  Issuing  Entity.  Each
Servicer has provided a statement of compliance with its  obligations  under the
servicing agreement  applicable to such Servicer (a "Compliance  Statement") for
the  period  covered  by this Form 10-K,  in each case  signed by an  authorized
officer of the related  servicer.  Each  Compliance  Statement is attached as an
exhibit to this Form 10-K. None of the Compliance  Statements has identified any
instance where the related Servicer has failed to fulfill its obligations  under
the applicable servicing agreement in any material respects.


                                     PART IV

ITEM 15.       EXHIBITS, FINANCIAL STATEMENT SCHEDULES.

        (a)(1) Not Applicable.

        (a)(2) Not Applicable.

        (a)(3) Not Applicable.

        (b) Exhibits.


<PAGE>

EXHIBIT
NUMBER                                           DESCRIPTION
------------    ----------------------------------------------------------------

3.1             Certificate of  Incorporation  of Residential  Funding  Mortgage
                Securities  I, Inc.  (incorporated  by  reference  to the Annual
                Report on Form 10-K for the  period  ended  December  31,  2006,
                filed by RFMSI  Series  2006-S1  Trust with the  Securities  and
                Exchange Commission).

3.2             Bylaws  of  Residential  Funding  Mortgage  Securities  I,  Inc.
                (incorporated by reference to the Annual Report on Form 10-K for
                the  period  ended  December  31,  2006,  filed by RFMSI  Series
                2006-S1 Trust with the Securities and Exchange Commission).

10.1            Series Supplement,  dated as of August 1, 2006, and the Standard
                Terms of Pooling and  Servicing  Agreement,  dated as of June 1,
                2006, among Residential  Funding Mortgage Securities I, Inc., as
                company,  Residential Funding Company, LLC (formerly Residential
                Funding Corporation), as master servicer, and U.S. Bank National
                Association, as trustee (incorporated by reference to the Report
                on Form 8-K filed by the Issuing  Entity with the Securities and
                Exchange Commission on September 8, 2006).
10.2            Assignment and Assumption Agreement, dated as of August 24, 2006
                between Residential Funding Company,  LLC (formerly  Residential
                Funding Corporation) and Residential Funding Mortgage Securities
                I, Inc.  (incorporated  by  reference  to the Report on Form 8-K
                filed by the Issuing  Entity with the  Securities  and  Exchange
                Commission on September 8, 2006).
10.3            Custodial   Agreement,   dated  as  of  August  1,  2006   among
                Residential Funding Company,  LLC (formerly  Residential Funding
                Corporation),  as master servicer,  Residential Funding Mortgage
                Securities  I, Inc., as  depositor,  Wells Fargo Bank,  National
                Association,  as custodian,  Goldman Sachs Mortgage Company,  as
                seller, and U.S. Bank National Association, as trustee on behalf
                of the RFMSI Series 2006-SA2 Trust (incorporated by reference to
                the exhibit with the same numerical  designation included in the
                Report  on  Form  8-K  filed  by the  Issuing  Entity  with  the
                Securities and Exchange Commission on September 8, 2006).
31.1            Certification of Residential  Funding  Company,  LLC pursuant to
                Rule  13a-14(d)/15d-14(d)  under the Securities  Exchange Act of
                1934.

33.1            Report on Assessment of Compliance  with  Servicing  Criteria of
                Residential Funding Company, LLC as of December 31, 2006 and for
                the period covered by this Form 10-K.

33.2            Report on Assessment of Compliance  with  Servicing  Criteria of
                GMAC  Mortgage,  LLC as of December  31, 2006 and for the period
                covered by this Form 10-K.

33.3            Report on Assessment of Compliance  with  Servicing  Criteria of
                Homecoming  Financial,  LLC as of December  31, 2006 and for the
                period covered by this Form 10-K.

33.4            Report on Assessment of Compliance  with  Servicing  Criteria of
                U.S. Bank National  Association  as of December 31, 2006 and for
                the period covered by this Form 10-K.

33.5            Report on Assessment of Compliance  with  Servicing  Criteria of
                Wells Fargo Bank,  National  Association as of December 31, 2006
                and for the period covered by this Form 10-K.

34.1            Attestation Report of  PricewaterhouseCoopers  LLP on Assessment
                of Compliance  with Servicing  Criteria  relating to Residential
                Funding Company, LLC.
34.2            Attestation Report of  PricewaterhouseCoopers  LLP on Assessment
                of Compliance with Servicing Criteria relating to GMAC Mortgage,
                LLC.
34.3            Attestation Report of  PricewaterhouseCoopers  LLP on Assessment
                of Compliance  with Servicing  Criteria  relating to Homecomings
                Financial, LLC.

34.4            Attestation  Report  of  Ernst &  Young,  LLP on  Assessment  of
                Compliance  with  Servicing   Criteria  relating  to  U.S.  Bank
                National Association.

34.5            Attestation Report of KPMG, LLP on Assessment of Compliance with
                Servicing  Criteria  relating  to  Wells  Fargo  Bank,  National
                Association.

35.1            Servicer  Compliance  Statement of Residential  Funding Company,
                LLC.

35.2            Servicer Compliance Statement of GMAC Mortgage LLC.
35.3            Servicer Compliance Statement of Homecomings Financial, LLC.

        (c)    Not Applicable

<PAGE>


                                   SIGNATURES

Pursuant to the  requirements of Section 13 or 15(d) of the Securities  Exchange
Act of 1934,  the  registrant  has duly  caused  this report to be signed on its
behalf by the undersigned, thereunto duly authorized.

Date:  March 26, 2007
                               RFMSI SERIES 2006-SA2 TRUST

                               By:  Residential Funding Company, LLC,
                                      as Master Servicer

                                      By:  /s/ Anthony N. Renzi
                                           --------------------
                                           Name: Anthony N. Renzi
                                           Title:Managing Director





<PAGE>


                                INDEX TO EXHIBITS
EXHIBIT
NUMBER                                           DESCRIPTION
------------    ----------------------------------------------------------------

3.1             Certificate of  Incorporation  of Residential  Funding  Mortgage
                Securities  I, Inc.  (incorporated  by  reference  to the Annual
                Report on Form 10-K for the  period  ended  December  31,  2006,
                filed by RFMSI  Series  2006-S1  Trust with the  Securities  and
                Exchange Commission).

3.2             Bylaws  of  Residential  Funding  Mortgage  Securities  I,  Inc.
                (incorporated by reference to the Annual Report on Form 10-K for
                the  period  ended  December  31,  2006,  filed by RFMSI  Series
                2006-S1 Trust with the Securities and Exchange Commission).

10.1            Series Supplement,  dated as of August 1, 2006, and the Standard
                Terms of Pooling and  Servicing  Agreement,  dated as of June 1,
                2006, among Residential  Funding Mortgage Securities I, Inc., as
                company,  Residential Funding Company, LLC (formerly Residential
                Funding Corporation), as master servicer, and U.S. Bank National
                Association, as trustee (incorporated by reference to the Report
                on Form 8-K filed by the Issuing  Entity with the Securities and
                Exchange Commission on September 8, 2006).
10.2            Assignment and Assumption Agreement, dated as of August 24, 2006
                between Residential Funding Company,  LLC (formerly  Residential
                Funding Corporation) and Residential Funding Mortgage Securities
                I, Inc.  (incorporated  by  reference  to the Report on Form 8-K
                filed by the Issuing  Entity with the  Securities  and  Exchange
                Commission on September 8, 2006).
10.3            Custodial   Agreement,   dated  as  of  August  1,  2006   among
                Residential Funding Company,  LLC (formerly  Residential Funding
                Corporation),  as master servicer,  Residential Funding Mortgage
                Securities  I, Inc., as  depositor,  Wells Fargo Bank,  National
                Association,  as custodian,  Goldman Sachs Mortgage Company,  as
                seller, and U.S. Bank National Association, as trustee on behalf
                of the RFMSI Series 2006-SA2 Trust (incorporated by reference to
                the exhibit with the same numerical  designation included in the
                Report  on  Form  8-K  filed  by the  Issuing  Entity  with  the
                Securities and Exchange Commission on September 8, 2006).
31.1            Certification of Residential  Funding  Company,  LLC pursuant to
                Rule  13a-14(d)/15d-14(d)  under the Securities  Exchange Act of
                1934.

33.1            Report on Assessment of Compliance  with  Servicing  Criteria of
                Residential Funding Company, LLC as of December 31, 2006 and for
                the period covered by this Form 10-K.

33.2            Report on Assessment of Compliance  with  Servicing  Criteria of
                GMAC  Mortgage,  LLC as of December  31, 2006 and for the period
                covered by this Form 10-K.

33.3            Report on Assessment of Compliance  with  Servicing  Criteria of
                Homecoming  Financial,  LLC as of December  31, 2006 and for the
                period covered by this Form 10-K.

33.4            Report on Assessment of Compliance  with  Servicing  Criteria of
                U.S. Bank National  Association  as of December 31, 2006 and for
                the period covered by this Form 10-K.

33.5            Report on Assessment of Compliance  with  Servicing  Criteria of
                Wells Fargo Bank,  National  Association as of December 31, 2006
                and for the period covered by this Form 10-K.

34.1            Attestation Report of  PricewaterhouseCoopers  LLP on Assessment
                of Compliance  with Servicing  Criteria  relating to Residential
                Funding Company, LLC.
34.2            Attestation Report of  PricewaterhouseCoopers  LLP on Assessment
                of Compliance with Servicing Criteria relating to GMAC Mortgage,
                LLC.
34.3            Attestation Report of  PricewaterhouseCoopers  LLP on Assessment
                of Compliance  with Servicing  Criteria  relating to Homecomings
                Financial, LLC.

34.4            Attestation  Report  of  Ernst &  Young,  LLP on  Assessment  of
                Compliance  with  Servicing   Criteria  relating  to  U.S.  Bank
                National Association.

34.5            Attestation Report of KPMG, LLP on Assessment of Compliance with
                Servicing  Criteria  relating  to  Wells  Fargo  Bank,  National
                Association.

35.1            Servicer  Compliance  Statement of Residential  Funding Company,
                LLC.

35.2            Servicer Compliance Statement of GMAC Mortgage LLC.
35.3            Servicer Compliance Statement of Homecomings Financial, LLC.