My roommate was really cold all of a sudden teeth were chattering, we were inside and the room was warm. what does this mean?

He may be sick: He may be coming with an infection and getting fever.If it continues he should see a doctor.

Fever: Sounds very likely that your roommate has a fever. A fever makes the body warmer so the room will feel colder to the body. With a bad fever, it feels like it's almost impossible to get warm. I would advise going to the md as soon as possible.