I think it's safe to assume that Thompson at least tried to shop Roman around. Otherwise, he would not have kept him around so long. But as others have said, you can't get much in return for a guy who looks like he's going to be cut anyway. Had Roman stayed, he would've been a cancer. That was obvious to everyone in the league.
I won't miss Roman, but I think some of you guys are exaggerating when you call him the "matador" and all that stuff. It's easy to criticize DB's for missing a lot of tackles, because almost all DB's, including some of the best, miss a lot of tackles. They are the smallest guys on the defense, and by the time the RB's get to them they've built up a full head of steam. Also, a lot of tackles by DB's need to be made in the open field, which is much more difficult than when a DL or LB can zero in on a ballcarrier who has no escape and really slam him.
Having said that, I will happy to have a guy back there who is more of a hitter. I can't say it enough times: I really like the way this defense is shaping up.