I see a lot of people complaining that Roomster "tricked" them by charging them $30 after their 3-day trial, but it clearly states that you have to cancel your subscription once it ends to avoid future charges. I feel pretty bad for the bad rep this company has. I don't think they are trying to con you at all. Btw, Roomster isn't the only company to do auto-renewal post trial. I know from experience. It sucks being caught-off guard, but if you're smart, you won't let it happen to you again. I know I'll be cancelling on time.
Anyway, I think it's important for someone to read this. Don't trust Craigslist links and if you are doubting whether a post is real, contact the person through Facebook if they offer it. You might even have mutual friends! Good luck.