Other account on iPad

I sync my iPad up with a computer in my house that my roommate occasionally uses, one time he wanted to sync his iPad up to that computer so he plugged in and grabbed a couple movies from my itunes. Now when I go to update Apps on my iPad, it sometimes prompts me for his password like he's the account logged in. When I go to settings for iCloud and iTunes/App Store my account is the one signed in and I don't even see his email anywhere in the settings. So I can't even find it to delete it. I tried resetting the ipad, but the same thing happened when I synced up to that computer again.

Clearly his account is linked with the iTunes on that computer and when I sync up it puts his information on my iPad, but is there any way I can delete it from my iPad? And I probably need to go into iTunes on that computer and delete his info as well, how do I do that?