My positional breakdown for a 100 injury league.
QB 2
RB/FB/TE 8
WR 5
OL 12
P 1
K 1
DL 7
LB 8
DB 9
I list RB, FB & TE together because they are interchangeable.
I carry 12 offensive linemen so I have a backup at all 5 positions plus a 3rd center and 3rd guard/tackle.
That leaves
27 offense
2 special teams
24 defense
Obviously you can drop an OL and add a DL if you want to make the offensive & defensive split closer at 26-25.
When setting your depth chart for RB, list all your RBs first then your FBs, TEs or possible QBs so you have at least 6 players on your RB depth chart and the A.I. doesn't have a chance to substitute a WR at RB by mistake.
Just sharing how I do it....it's not the only way and I would love to hear how others do it but when you have a rule where no WRs can run the ball, you must have enough active depth at RB to avoid the A.I. putting you in violation.
I carry less defensive players because I use LBers as deep depth for DL, DBs as deep depth for LBs. I almost always carry a minimum of 9 DBs so I have 5 CBs, 2 SS & 2 FS.