For me it comes to Duke Williams vs Isiah McKenzie as the bubble WR.
When I look at 25 players on offense for the roster, I see:
2 QB (Allen, Barkley)
4 RB (McCoy, Gore, Singletary, Perry)
1 FB (DiMarco)
5 WR (Jones, Beasley, Brown, Foster, Roberts)
3 TE (Lee, Dawson, Sweeney)
5 OL (Dawkins, Spain, Morse, Ford, Ty Nscke)
I assume Tyler Kroft will start on PUP or go on IR for coming back later.
That is 20 players covered and I believe are safe unless we trade McCoy or one of Jones or Foster. Now we have to break up the 5 remaining spots as
3 OL, 1 WR, 1 RB
3 OL, 2 WR
3 OL, 1 WR, 1 TE
or
4 OL, 1 WR
The extra WR currently seems to be McKenzie's to lose based on his play in the pre-season. He also can do Punt return
The only way I see Duke Williams getting in is if the Bills go with the 3 OL and 2 WR option.
The 3 backup OL appears to be Feluciano, Wesley and Teller.
Robert and Perry make the team on Special Teams.
The curious situation is going to be that even if the above make the roster, most likely McKenzie, Williams and even Singletary may not make it to list of 44 players who are active on game day.