for RB I'd go with D.Will and Harrison. Harrison has a great matchup, Cleveland looks to be a run first team and tampa will not put up a lot of points right out of the gate. Harrison is the main back there and will get a lot of carries. D. Will is a playmaker and has shreadded the Giants in the past. Forte would be next in line, but the bears are going to throw a lot. If this is a PPR league, forte gains a little more value, but I would still take harrison and d. will, especially with j. stew being somewhat limited with a heal injury.
both cowboys backs are out for me as we don't know who will get the bulk of the carries.
for the WR spot, I'd go with Knox, as stated above, the bears will throw a lot and Knox has way more upside. He should be the #1 reciever there, but you never know how the passes are going to be distributed. i wouldnt go with Lee evans as I think the Fins are going to control the clock, but I see the bills throwing as I figure they'll be down, but I think Knox still looks better. Gaffney would be a nice choice, he had some great games at the end of the season last year, if you don't like Knox, I'd roll with Gaffney.