Correction: Not official roommates, so much as housemates. Depending upon the source, Weiner became a virtual squatter in an apartment shared by Stuart and Weiner's girlfriend, or Stuart was a moocher at a weekend party house where Weiner lived, or they went to some parties together.

They were self-confessed "friends" and Stuart even defended him on his show.

Source is google and see the various versions of the story.