[Sony Ericsson Xperia Mini, Mini Pro, Xperia Pro, A] Mr.Its:
I looked into it and it's a flashtool saftey feature. It stops you from flashing the wrong ROM data to your phone. It can often be bypassed by using an older version of flashtool, as seen in this thread where flashtool 0.6.7.0 did the trick. You just need to remember to wipe your data, so make sure you have a backup first.

I'd test it myself but as I no longer have the phone I wouldn't want to tell my less tech-savvy friend to do it as then it'll be a nightmare to put right.

I found a list of networks within the baseband and Rogers is there, but I don't know if it's GSM or not.

mobi*
CELL +
CPV T+
HOLA PARAGUAY S.A.
BTC MOBILITY LTD.
I.C.E.
CAN Rogers Wireless Inc.
BAKCELL GSM 2000
HT - 200
TH GSM 1800
MM 900
TH ACT 1900
ACT-1900
USA 340
movistar ?GSM 850
Test PLMN 1-1
Test1-1
Test PLMN 2-1
Test2-1
606 01
62401
GNQ01
432 11
INDH1
FL1
Test PLMN 1-2
Test1-2
T-2
HR TELE2 HR 21902
CIV02
Far East RUS 12 250 12
RUS 12
LV TELE2
YUG 03
45703
YUMTS YUG03
454-15
RUS16 250 16
SingTel-G18
life:
Orange A
NL-RCA
MTN-UGANDA
CYTAVODA
IDEA
cellular at SEA
AVEA
ZAIN GA
EMTS NGA
MTC NAMIBIA
TELIA
AMAZONIA
VOILA
OLA
DZA NEDJMA
TELMA
TMA
tiGO GHANA
TUNISIANA
TUNSIANA
CLARO ARGENTINA
IRAQNA
UNIQA
STELERA
FI SONERA
CAMBODIA SHINAWATRA
3TELSTRA
MTN-SA
VodaCom-SA
GETESA
mobily-KSA
CENT USA
Wilkes USA
Iowa Wireless USA
HPGYSA
IND TATA
3 ITA
Beeline UA
APUA PCS ANTIGUA
KT VIVA
NOVA
KT WATANIYA
TW MOB
Vip SRB
Telenor SRB
STARHUB
EWB
A M C
Cell C
ACSIAC
Hutchison MAC
TH-DTAC
USA ASTAC
CTBC
CMCC
AF AWCC
JAM DC
DK TDC
USAEC
TMIC
CLARO NIC
ClaroNIC
MONGOLIA UNITEL LLC
COL_TEMC
PLWPMC
GPC
WARID RC
CELTEL RC
CELTEL DRC
WARIDRC
RUS DTC
FSMTC
NTC
STC
BWC
TMO D
T-Mobile D
WARID BD
SCELL CD
VODACOM CD
CELTEL TCD
Vip MKD
HK NEW WORLD
Orange MD
M-AND
STA-MOBILAND
CLARO HND
CELTELHND
ClaroHND
I WIND
ATL-VOD
IT&E
GLOBE
PACE
INA SPICE
RELIANCE
IR MTCE
BEELINE GE
IL ORANGE
RO ORANGE
voda IE
vodafone IE
CHIPPIE
CHINA MOBILE
BPL MOBILE
OMAN MOBILE
U MOBILE
D-MOBILE
JPN EMOBILE
MV DHIMOBILE
VUT SMILE
BEELINE
JAWWAL-PALESTINE
ZW NET*ONE
FJ VODAFONE
CYTAMOBILE-VODAFONE
SOMAFONE
VN MOBIFONE
PK-UFONE
VN VINAPHONE
CELLONE
NETONE
CURE
3 SE
SpringMobil SE
Telenor SE
BITE
C-OTE
RO COSMOTE
GR COSMOTE
SWE
SI BREEZE
SN ALIZE
Orange F
MTN AF
TEMPO-AF
KR KTF
DigicelF
32G
MY CELCOM 3G
Sweden 3G
H pannon 3G
INDIGO-3G
TIME3G
Sweden3G
pannon3G
M-Tel BG
TMO CG
T-Mobile CG
MTN-CG
voda EG
vodafone EG
KI-FRIG
ZAIN MG
MTN - NG
Zain NG
Glo NG
MTN-NG
ROAMING
ZONG
Digicel PNG
SRI DIALOG
SN-SENTEL SG
MTN-UG
TeleG
TMO H
T-Mobile H
UMNIAH
zain BH
orange CH
BH GSMBIH
Globe Telecom-PH
IR KISH
IDEA TAMILNADU & CHENNAI
TWN MOBITAI
MTN CI
Orange CI
ACELL-CI
NECCI
USAC1ECI
GCI
ICOM TCI
Is.Com TCI
IslandCom TCI
IR-TCI
USACWCI
ONATEL BDI
TELECEL-BDI
F-VINI
MOVISTARNI
HURI
USAACSI
PTSI
MAGTI
GN LAGUI
CCTBVI
PROXI
BEELINE TJ
3 DK
TELIA DK
KOREK
3 HK
C&W FLK
TMO MK
T-Mobile MK
Telenor PK
ETL MOBILE NETWORK
O2 - SK
TMO SK
Orange SK
T-Mobile SK
ETK
O2 - UK
3 UK
PMN UK
TMO UK
C&W UK
voda UK
T-Mobile UK
vodafone UK
Opal UK
Cable&Wireless UK
O2 -UK
AMC - AL
EAGLE AL
voda AL
vodafone AL
AR PERSONAL
ESV PERSONAL
JAWWAL
MOBNCL
GINCL
PCL
LS-ECONET-EZI-CEL
CUBACEL
GAB TELECEL
NE TELECEL
DIGICEL
UNICEL
TELCEL
GAMCEL
COMCEL
AIRCEL
T-SEL
IND TELKOMSEL
SYRIATEL
ONATEL
GIBTEL
MOBITEL
MOR MEDITEL
DIGITEL
MALITEL
UNITEL
BGD AKTEL
ZM CELTEL
EMTEL
ZANTEL
SENTEL
TUNTEL
IND AIRTEL
SIR AIRTEL
SEZ AIRTEL
MR MATTEL
VNM and VIETTEL
RWTEL
BYTEL
CPV MOVEL
CMOVEL
Orange FL
Swiss FL
SwisscomFL
CLARO CHL
ClaroCHL
TDC MOBIL
SI TUSMOBIL
LATMOBIL
C1AMARIL
TIM BRASIL
TELEMOVIL
GSMTKL
U-CALL
KALL
TM CELL
TG-TOGO CELL
STAR CELL
R-CELL
ASIACELL
MD MOLDCELL
MDCELL
TGCELL
TASHICELL
BDI TEMPO-AFRICELL
KZ KCELL
BKCELL
TR TURKCELL
GEO-GEOCELL
STARCELL
SCELL
TCELL
TXCELL
ORANGE ML
MALITEL ML
OML
TMO NL
voda NL
Orange NL
T-Mobile NL
vodafone NL
TIGO COL
POL
Orange PL
TELE GRL
O2 - IRL
O2 IRL
3 IRL
CELTEL SL
MILLICOM SL
CSL
BTL
BRA SCTL
BDITL
UTL
BG GLOBUL
IND XL
EGY MobiNiL
Babilon-M
Beeline AM
MTN CAM
Orange CAM
MOR IAM
MTCNAM
MOBITEL - KHM
MT-KHM
I TIM
OPTIM
TNM
SAF-COM
VODACOM
MEGACOM
ISLACOM
BBCOM
TUNISIE TELECOM
MILLICOM
MY CELCOM
SAHELCOM
BY VELCOM
BW MASCOM
CLARO DOM
ClaroDOM
MTS ARM
PORTA GSM
LT BITE GSM
TH GSM
GIBTEL GSM
DIGITEL GSM
AZE - AZERCELL GSM
ANT CURACAO TELECOM GSM
LAO GSM
SETAR GSM
AKOS GSM
DMTS GSM
CT GSM
LMT GSM
Telecel GSM
Mx Telcel GSM
Telcell GSM
TWN TransAsia Telecom GSM
Celcom GSM
TA-GSM
FT-GSM
CU-GSM
RUS Kuban-GSM
SR.TELESUR.GSM
SGP-M1-3GSM
PORTAGSM
SETARGSM
MPTGSM
CHN-CUGSM
KUGSM
L LUXGSM
iCAN_GSM
Telecel_Bolivia_GSM
Comcel_GSM
MTS TM
CTM
CLARO GTM
Claro GTM
CLAROGTM
ClaroGTM
GM COMIUM
GMCOMIUM
TWM
MTN ZM
Network Norway N
MTC LIBAN
USA i CAN
USA iCAN
ROSHAN
OMAN
RUS_SCN
MobiTel SDN
TLCL-BEN
SWEDEN
CANFN
Orange GN
ORANGEGN
CellcomGN
Vodafone IN
ZAIN
IN-DOLPHIN
CAMSHIN
TELECEL BENIN
MTN BENIN
UNTLMN
PMN
P TMN
SABAFON
MKD COSMOFON
SFR REUNION
BELL BENIN COMMUNICATION
NL KPN
COG MTN
GH MTN
ETH-MTN
ET-MTN
Swazi-MTN
SwaziMTN
KP SUN
NetworkN
TIGO LAO
VIBO
MONACO
BATELCO
MAGTI-GSM-GEO
NEO
Samoatel GO
RUS INDIGO
YOIGO
COL MOV / TIGO
LI TANGO
L TANGO
TELECEL-TOGO
tiGO
MIO
Orange JO
zain JO
JP DOCOMO
TMO
RO Vodafone RO
VF-RO
CLARO
VIVO
KIFZO
voda P
vodafone P
MCP
STARHUB-SGP
HR VIP
USASXLP
AR TP
zain IQ
S COMVIQ
CLARO AR
ALMADAR
MOVISTAR
UA-KYIVSTAR
OUTREMER
EASTER
F SFR
TIM GR
voda GR
vodafone GR
T-Mobile HR
MTS UKR
D-HARBOR
IRL - METEOR
TELENOR
VODAFONE TR
VF TR
SYR MOBILE SYR
TELIA S
ORANGE BS
Orange BS
W 2000 PCS
Wireless 2000 PCS
CL ENTEL PCS
AmeriLink PCS
AirLink PCS
Einstein PCS
APUA-PCS
NWPCS
voda ES
vodafone ES
WILKES
CMCC PEOPLES
NOVA IS
NCL MOBILIS
MG ANTARIS
SPM AMERIS
CD OASIS
DJ EVATIS
MDA EVENTIS
628 01/LIBERTIS
MY MAXIS
UA-KS
Vodacom-LS
GUY CLNK PLS
NZ COMMS
CADCOMMS
VMS
ROGERS
FARMERS
SCGTS
UZB MTS
ARM MTS
DMTS
RUS15 RUS SMARTS
RUS 07 RUS SMARTS
P OPTIMUS
BEL PROXIMUS
SCS RUS 05 RUS SCS RUS
SIBCHALLENGE RUS
ETK RUS
MegaFon RUS
MTS-RUS
YES OPTUS
iSmartUS
IWS
ACeS
TelenorS
AT&T
INDIGO-T
3 AT
Orange AT
ETISALAT
IND INDOSAT
INMARSAT
DRC and CCT
FET
CK KOKANET
VE_MOVILNET
SUNNET
BDI ECONET
ZW ECONET
UA-GT
3GT
KGT
CHT
voda IT
vodafone IT
SKT
OMNITEL LT
TJK MLT
3GT MT
voda MT
vodafone MT
FI AMT
RUS BMT
EE EMT
LV LMT GSM LV LMT
OMT
SMT
ANT
USABIGFOOT
SMART
RF FAR EAST
FIRST
BeST
TLS-TT
TSTT
TLXT
voda AU
vodafone AU
US PLATEAU
voda HU
vodafone HU
L VOX.LU
SFR RU
TIM PERU
EMTEL-MRU
CELLPLUS-MRU
MTU
MOTIV
BITE LV
CLARO SLV
ClaroSLV
BOMOV
C&W
PCCW
PANCW
USANCW
Zain KW
zain KW
CELTEL MW
ETLMNW
HPW
BTW
WVW
TELECEL ZW
IMMIX
TELEMETRIX
MANX
CLARO URUGUAY
MTS BY
BeST BY
C&W SEY
BSKY
CLARO PY
USA SIMMETRY
MOBILITY
CLARO UY
YemYY
EUROTEL - CZ
ET - CZ
TMO CZ
T-Mobile CZ
Vodafone CZ
BITEL KGZ
Beeline KZ
NEO-KZ
VodaCom-MZ
voda NZ
vodafone NZ
Telecom NZ
MOBITEL - TZ
Hits TZ
ZANTEL-TZ
Beeline UZ
KoZ
GNAreeba
SMC-Voda
USA - Extended Area
alfa
Digicel Tonga
T-Mobile Austria
Libyana
dna
Carolina
Era
Telstra
EE elisa
FI elisa
Chunghwa
Thuraya
Iran Taliya
AeroMob
uiutils.c
TELE Greenland
CHE Tele2 Switzerland
USA Mid-Tex Cellular Ltd
Reliance
o2 - de
voda de
Vodafone.de
F-Orange
orange
F?roya Tele
LBN OGERO Mobile
TW Mobile
Telstra Mobile
Manx Telecom Mobile
BT B-Mobile
T-Mobile
PNGBMobile
BGD bMobile
AeroMobile
go mobile
b-mobile
BRU-bmobile
gomobile
Yorkville
NAM Cell One
Cellular One
CellOne
USA - CellularOne
RUS Beeline
KGT-Online
SmarTone
Far EasTone
Airtel-Vodafone
SmarToneVodafone
Carolina Phone
In&Phone
GrameenPhone
IL Pelephone
Yorkville Telephone
US - Union Telephone
CCT Boatphone
Orange re
Sure
sunrise
KL-Frigate
ProMonte
JT-Wave
Etisalat Af
Viking
tele - ring
telering
Spring
Hutch
Epic Touch
EpicTouch
GH ONEtouch
DiGi
Oi
Digi
SoftBank
AmeriLink
NationLink
AirLink
WestLink
Banglalink
Mobilink
Chinook
PY Personal
West Central
BrTCel
BaTelCel
MOZ - mCel
LamarCel
M-Tel
WaridTel
SingTel
MobiTel
UG CelTel
UnionTel
IND AirTel
Telecel
Digicel
USA Unicel
Aircel
m:tel
NG Mtel
Qat - Qtel
Utel
vivatel
Mobitel
Uraltel
BF Celtel
celtel
Mobiltel
IND Airtel
STP CSTmovel
RO Digi.Mobil
Si.mobil
LBR Lonestar Cell
PINECell
IS-IceCell
BaTelCell
UZB Ucell
Vivacell
Telcell
MTN Irancell
ClaroJam
MCP Maritime Com
BRU-DSTCom
VodaCom
MN MobiCom
SunCom
PetroCom
N NetCom
KOR SK Telecom
FSM Telecom
Uganda Telecom
Chunghwa Telecom
Norfolk Telecom
F-Bouygues Telecom
Safaricom
Celcom
IL Cellcom
Somoncom
Swisscom
GSM Telkom
SO Telesom
Telsom
Grameen
GH Zain
Einstein
GloBenin
Siminn
SabaFon
MegaFon
Sonofon
Babilon
RL MTC Lebanon
H pannon
Monaco
Cell One of NE Colorado
Fido
SRI - Tigo
Indigo
Yoigo
Vodacom Lesotho
glo
hello
Cell One Amarillo
PR Claro
AZ Nar
Libya Al Madar
Almadar
Cingular
BRA BrTCelular
Pine Cellular
PH Sun Cellular
Lamar Cellular
Texas Cellular
LoneStar
B Mobistar
B mobistar
AR - Movistar
COL Movistar
movistar
Jasper
OnAir
USA Dutch Harbor
N Telenor
nawras
Navitas
On-waves
ALG Mobilis
Som Golis
Oasis
axis
NZ Comms
High Plains
Centennial Communications
Blue Sky Communications
Cable & Wireless
USA XIT Wireless
West Virginia Wireless
Stelera Wireless
West Central Wireless
Corr Wireless
USA - Immix Wireless
E-Plus
Optus
Etisalat
etisalat
INX Inmarsat
F - Contact
Sprocket
Seanet
Movilnet
USA - Commnet
USA Pinpoint
iSmart
NL Tlfrt
NL Telfort
RF FEast
3 Macau
HT Macau
SmarTone Macau
du
Mid-Tex
Play
Blue Sky
mobily
Djezzy

Thanks to both of you for the info so far :)