I have personally done the best friend/roommate role play before. I enjoyed it mainly due to the way it played out. There was A LOT of sexual tension between the 2 roommates, but we did it in a comical way. There was a friend of the males that we affectionately called the cock block. For instance, Beth lost her wallet and she couldn't pay to get Zeus, her Chihuahua, from the vet because she couldn't pay her bill. So, the whole day went back and for with Beth and Sal trying to find her wallet, which of course they did, and she was able to bring Zeus home. They are sitting on the couch together, Beth laying with her back against Sal's chest, and they are having one of those really intense moments. Sal leans in to kiss her and in comes Zack, ruining the moment.
Beth and Sal eventually do hook up, and I know this is a bit sitcomish, but it was a lot of fun. I would love to do another RP like that. So let me know if you're interested. :)