If we let Roy go and he signs with another team like Orlando, LA, OKC, or Chicago, I will renounce my Blazers fandom and be glad to cheer him trouncing the Portland Trailblazers every year in the Playoffs.
Roy is one of the nicest guys in the game but also has the killer instinct seen in HOF guards. And so, when you cross that killer instinct by betraying him, you'll never ever earn his respect again.
EDIT: I mean, shoot, if you let him go, he doesn't even have to play right now. He could wait until other contending teams are below the cap. You can add New Orleans, NY, Boston, Miami, San Antonio, Dallas, Houston, Minnesota to the list of teams who would want Roy as well.