that looks like an even trade but i am not sure because keyshawn isn't doing that well and alexander may be heating up as well as williams hot streak/luck may be ending. You wouldn't really have a backup rb if you take dunn since he is not performing that well and moss is in a slump + he has a bye week. I think galloway will put up good numbers along with rice so my final advice is do not trade.
I should have added my roster because I am really not sacrificing anything in terms of depth. My roster is as follows:
RB: Alexander, Staley, Henry
WR: Rice, Galloway, Moulds, Owens, D. Terrell