Can I still take an OTA after I unlock and root?
Answer: On Android versions 5.*.* and up, No. On KitKat (4.*.*) , yes (sometimes) – if you haven’t made any other system level modifications.
With android versions 5.*.* and up, the OTA update process checks the entire system blob. That means if just one small thing is different about the system partition the OTA will fail. Since rooting itself (regardless of the method: manual/toolkit) installs Superuser as a system app and su binaries to the system partition it inherently breaks OTA’s.
So how should you update a rooted Lollipop device?
1. Wait for the official factory package from google to be released for the build you would like to update to.
2. Backup your apps + data, as a safe measure – in case you end up having to wipe data.
3. Use “Flash Stock + Unroot” and “No-wipe mode” (to avoid a data wipe).
That’s it. Afterwards you can re-root.