Advice to SavePros321: Try to make up with your wife
Two things,
I was married once to a lovely and faithful girl. When we first went out, we were totally into each other and it was like a romantic fairy tale. However after our first date, she was pressured into going out on a date with someone else, and she gave in. It was only a friendly date without even a kiss on the cheek and after this one date she dropped it.
After we were an item I found out about this from her and I was upset and a bit shocked. She tried to explain and I eventually dropped it. What I can tell you is that during the 9 years we were together she was incredibly faithful and devoted to me. One of the main reasons the marriage fell apart was because I was not faithful to her and have always wanted to sleep with other women. So give your wife a chance, it was long in the past.
Another thing, I am saying this to help you and not upset you, if you are upset by my following observations, which may be inaccurate, I apologize. It sounds like you were a bit jealous of your old roommate, and the thing you liked in those days about your current wife is that she did not fall for your roommate, so this was your victory over him, finally after watching him take the prize again and again. So when you found out they were together at some point, this is what really upset you and hurt your ego.
If you really love your wife and want to make it work out, forget about it, if you do not you will wreck your marriage.