I had a friend in the same position as your bf. Ultimately, she spoke up, the roommate went mia, never paid her back, their friendship cut off AND she stopped talking to me. I guess what I learned from the whole thing is that people are going to do what they are going to do regardless of what we say. Even in the most caring way that we say it.

After we express our opinion, observations, boundaries once or twice, it is time to look at ourselves and what we can do to best take care of ourselves - and not try to focus on or change someone else's business. No matter how much we care. best wishes to you.

(remember, you come first in this equation)