。
I'm Paul, your roommate.
Literal
I [topic-は] you [possessive-の] roommate [possessive-の] Paul [insistence-だよ].
A self-introduction. ルームメート is an English loanword. The の chain links 君のルームメート ('your roommate') to ポール — 'Paul, who is your roommate.' だよ adds casual assertion.