Trade value of Big Ben in 14 team league

[ralphkins 0]

I lost Ronnie Brown and need a solid RB badly. I have Westbrook, Sammy Morris, and just picked up Kenton Keith. I want to ditch Roethlisberger to free up some room on my team as I have Griese on my bench. What tier RB should I go after in my trade proposals? Or should I go after a WR and package him with one of Coles, Boldin, Berrian, Branch, and Walter?