Give it some time! I know it’s super hard and you don’t want to hurt any feelings, but if something is bugging you (like hogging all the space or taking all your stuff w/out asking), just tell your roommate the truth. Also give it a couple of weeks and if you think you ABSOLUTELY cannot live with your roommate, ask for a switch. Remember, you and your roommate do NOT have to be friends. Just compatible.
Super super tiring but totally worth it! I really like all my professors. They are soo so cool and interesting and super badass.