Is this a college roomate? If so, i'd use grades, majors and their class/work schedule for comparison.
If this is just a regular roomate, haha, i wouldn't use a online roomate thingy. Did you ask all your friends and relatives to see if any of them or THEIR extended friends' or relatives needed a roomate?
Plus, if this is just for a regular roomate, then I'd ask what their work schedule is like and their career, but there are still some psychos who are pretty smart and successful, lol...except that they might smoke crack at like 4am in the morning, hahaha.