I have had some goo friendship develop from contact with roommates, and many who at least remain Facebook friends. but this relationships were cultivated by going against the isolation and difficult living circumstances found in a rooming house.
One of the things I do every year, to attempt to build community, is to try to involve roommates in some kind of Christmas celebration. I put up a creche set, I go by a tree. I break out the decorations and try to get a tree decorating party going with a little music. Maybe we watch a Christmas movie. I can do a little to impart my faith in this while respecting where others come from.
I also make coffee every morning to share with my fellow rooming house denizens. I very the coffee blend to keep it interesting. Sometimes we wind up drinking coffee together and talking. More on rooming house life at a latter date.