Roy is available? I wouldn't be too sad if Butler stayed... He'd be an impact player for us, if healthy.
While it's true what you say about both players (I too have serious doubts about Butler at SG), the nature of the knees in question are different...Butler's is expected to get better.
Butler might make Deng and his big contract expendable to a degree. But we've seen what happens when we lose a player, thinking its easy to find a replacement.