Any of these worth a Roster spot?

There are several GOOD receiving RBs on the WW, does any of them need to be owned? 0.5PPR. I currently have Riddick on my bench along with Martin, Perine, and Rawls (who i need to drop).
Bernard, Sproles, Thompson, Duke, J.Richard, Riddick, Sims? Also, Chris Johnson could be an interesting pick up with his Cardinals history??

Sproles and Richard are my favorites on this list.