Need some sit/start help for wk 1

I play in an 8-man league, 1 QB, 2 WR, 2 RB, 1 TE, 1 Flex. Standard Yahoo scoring, except there's also 1 point for every 10 return yards.

I need to decide which of the following players to start:

RB: Ray Rice (vs. Bengals)
RB: Chris Johnson (vs. Patriots)
RB: Steven Jackson (vs. Lions)
RB: DeMarco Murray (vs. Giants)
WR: Greg Jennings (vs. 49ers)
WR: Antonio Brown (vs. Broncos)
WR: Wes Welker (vs. Titans)
WR: Marques Colston (vs. Redskins)

So I need 2 RBs, 2 WRs, and a Flex player. What do you guys think? Will Antonio Brown be returning kicks for the Steelers? Will Welker be returning punts for the Patriots?

Thanks for your help!