Green’s Dictionary of Slang

(US campus) a room-mate.

1970		J. Bouton Ball Four 168: ‘Hang in there, Rooms. Tonight we’ll go out and celebrate until we forget what happened’.
1996		Eble Sl. and Sociability 101: In-group vocabulary often occurs in the optional form-of-address slot in a sentence, as in the use of rooms ‘roommate’ in ‘Rooms, will you take the trash out?’.