Restoring an image after root

I am going to root my son's phone ( Nexus 6 ), but he has tons of stuff on it. last night I ran a full backup via adb and created backup.adb

When I root the phone today, can I restore this back up so he still has all of his apps, purchases, music, etc..

I would just like to know if that's possible or will he lose most everything from apps like Kik and Whats App.

Thanks,
Nick

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