I think Cullen should get along well with Cassian and Steve, especially. He and Cassian both have experience with following orders until getting to a breaking point and realizing they can't anymore. Not that it's a conversation either of them is likely to have. He's very big on things in order, so he's tidy. He does have periodic nightmares but they shouldn't keep anyone up.
Keller will be not-at-all-bothered by Clarke not remembering her very well. >.> She'll also be not happy if she finds out Clarke was injured recently. She's also a pretty good roommate, provided people aren't freaked out by shifters.