Will restoring a backup unroot my rooted device again? I have made a full backup of my formerly unrooted android device using Android Debug Bridge, later rooted it and now would like to restore the backup while maintaining root access.

Will this work by restoring the backup with adb restore or will my phone possibly be unrooted (just like with a factory reset)?

Edit: My Samsung Galaxy Nexus GT-i9250 is currently running on Android 4.3, the backup was made with the same version using the command adb backup -apk -shared -all -f.

Update: I restored the update and my device is still rooted (checked with Root Checker from Super User), though a few apps and some data were not restored.
As long as you don't restore the system partition (I don't know whether this is backed up by ADB), your root access should be preserved.

You could just make a backup of the state of your device now and restore it, when needed.