Be clear and communicative. Being forthcoming with your own needs is just as important as being a good listener. Is something is bothering you, talk about it; if you just want some alone time, say so; if you are feeling overwhelmed and just need to vent to your roommate for a little while, ask if they have a few minutes. Roommates aren't mind readers, so it's important for you to communicate with your roommate in a genuine, clear, constructive way as often as possible.