I know that when it comes to things like exams or studying in general, I like to have someone who's a quiet roommate, and who wouldn't mind me staying up late. Because I wouldn't have met this person in advanced, I wouldn't feel comfortable "studying" (or practicing) with my roommate.
Perhaps Tate. As a psychic type trainer, he seems very quiet and reserved. Best thing yet, is that because he always likes practicing with his sister, there's a high likelihood that he would leave the room to be with her, allowing me to have peace and quiet all to myself.