[Nexus 7 General] dtg7:
Just thought I'd share, might help someone. This is for Nexus 7 previously bootloader unlocked and rooted (and whatever else, like xposed) going from 4.4.4 to 5. If you're not on 4.4.4 and bootloader unlocked get there first. Obviously you need usb debugging on.

You also need some form of adb and fastboot. I used Minimal ADB from here:

http://xdaforums.com/showthread.php?t=2317790

What I Did:

- Got the Lollipop OTA from the links posted everywhere by now, including the second sticky here in General.

Put a copy in the adb/fasboot folder in Windows, and renamed the file to updatelollipop.zip to make it easier to handle.

Tried old style of updating: Uninstall Xposed, flash Xposed Disabler, flash OTA zip from custom recovery. Failed. Tried again, failed again.

But this was expected, as I'd read that the way lollipop updates is different from all previous updates and will fail at the slightest discrepancy in system partition.

So, need clean system.

- Got the Stock 4.4.4 firmware from Google: https://developers.google.com/android/nexus/images

Inside the firmware file found the system.img and recovery.img images.

Put these two files in the same folder as minimal adb and fastboot.

- Got into bootloader.

if powered off hold power and volume down keys. if booted up in Minimal ADB command prompt window type:

adb reboot bootloader

- flashed stock system and recovery

fastboot flash system system.img

fastboot flash recovery recovery.img

- Got into stock recovery

In bootloader, scrolled to select recovery, then with "No Command" showing held power and clicked volume up.

Select apply update from adb. Screen says to type adb sideload update from computer.

Ran into a hiccup. ADB would not recognize my N7. typing "adb devices" returned empty result. Booted up into Android, computer and adb recognized device fine. typed adb reboot bootloader, and in bootloader adb no go.

So while connected to computer in bootloader mode, went into Device Manager in Windows. Sure enough there was unknown device called grouper. Promptly update the driver. I used driver files from the Wugfresh toolkit I had installed. The device was recognized as Google Galaxy Nexus ADB device. Didn't matter to me as long as it was recognized as ADB. If you want official drivers you can get them from Asus here: http://support.asus.com/Download.aspx?SLanguage=en&m=Nexus+7&p=28&s=2

- Back into ADB sideload screen in N7 stock recovery.

typed adb sideload updatelollipop.zip

Let the ADB push the file, then stock recovery did the update. no issues. back in recovery might as well erase cache partition.

Root then. Could use Wugfresh NRT but decided to go manual.

UPDATE: As of SuperSU 2.27 Beta, flashing SuperSU from custom recovery is enough to gain root on Lollipop 5.0. Root kernel is no longer needed!

Old fashioned root failed works now: get the latest twrp recovery (copied it into adb folder, renamed it to twrprecovery.img), get the latest superSU (put it anywhere in N7 internal storage), flash the latter with the former:

In command prompt, typed fastboot boot twrprecovery.img

this temp booted twrp. promptly went to install, found superSU zip, flashed it.

Booted into Android, Lollipop looks nice, but No Root.

Again, not surprised, had already read lollipop needs modified kernel for root. Looked in the Wugfresh NRT files, had two candidates, modified boot img and root kernel img. not sure the difference, but the two files had different file sizes, and I had read somewhere that modified kernel would keep most of the security features of stock kernel, only modifying permissions needed for root, so decided to go with the kernel img file. Copied it over to adb fastboot folder, renamed it rootboot.img

- got back into bootloader. in command prompt typed

fastboot flash boot rootboot.img

Rebooted into Android, had root! Great. Notice didn't need to flash superSU a second time.

To check if root works fine, just open superSU app. If it opens fine then you're good. Root apps will ask for root, and granting will work fine, but that doesn't mean the apps will be able to use root for the simple reason that they might need to be updated. for example, es file manager asked for root, was granted, but root directories showed empty. clearly needs an update. Tried Total Commander, gave root, worked fine. So apps ability to use root in lollipop will vary based on their need to be updated to work.

thanks as always to Wugfresh and Chainfire.