Should have been a D? Or are you expecting the 2 frosh to be lights out ?
Chaney is physically ready to be a legit P5 RB. That part shouldn't be debated by anyone with working eyes and a brain.
Mentally, RB is among the easiest positions to transition from HS to college. Coming from that archaic offense Belen runs, he will have some learning to do, sure. But as an EE with smarts and work ethic, I fully expect Chaney will be ready to meaningfully contribute this season.
A little less confident with Rooster. Physically, he's a smaller back and may need some S&C love. But he's also coming in early. I can definitely see a role for him as a pass catcher out of the backfield, as he seems to be a real natural receiver from that spot. I expect him to have some specialized packages and get some snaps.
On Burns, he's not the guy you want carrying the ball 15+ times a game. But a smart OC can find a role for him in the redzone and potentially some short yardage packages.
Cam's biggest problem appears to be his vision, but a change in OL blocking scheme and offense could make those things easier for him, too. Can't discount the effect of our ****** offensive scheme and playcalling on our RBs ability to carry the football.
Overall, I'd rate the RBs a B- right now, talent-wise, with potential to finish the season better than that.