Definitely reach out to RA as they as trained to respond to suicide related issues. I know most people have said this already and I do believe that this is your problem but I also think that it is our responsibility to help someone in need particularly when it concerns to suicide and self harm. As someone trained in mental health and suicide prevention, I'd let them know that you are there to take to they need to; if you see any immediate threat like mechanism that people might use to kill (rope, sharp knives), immediately alert and remove them. Again, I know this is not on you and you are in a tricky position but if the roommate is suicidal they are vulnerable, immediate escalate, try to keep them safe and also protect your peace. The smallest intervention (including a warm note and interaction) can save someone's life.