I agree with holding onto Tolbert simply because you own Mathews. If you didn't, I would say drop him.
On the trade, Clearly, CJ >>> Rice. But Marshall is >>>> Crabtree. What do your other WRs look like? Who are you starting? I will say, Rice's slow start and recent injury make me lean against the deal. I don't want to say that Rice is this year's Forte yet, but he hasn't done a whole lot the first 3 games. So unless you WRs are really hurting, I think you can pass on the trade.
12 Team League. We start 2 QBs and get .5 PPR, otherwise standard scoring
QBs: Stafford, Fitzpatrick, Collins
RBs: Charles, Mendenhall, Best, Starks, Carter, Karim
WRs: D. Jackson, Marshall, S. Smith, Green,
TE: Hernandez, Cook