Whether or not layer feed is hard on rooster's kidneys is commonly disputed on this site. I personally have no problems. A simple option is to feed all flock members a flock raiser feed (20% protein), and supply oyster shell for the layers, rather than keeping everyone separate. The roosters will not eat the oyster shell as long as they don't need it. Supplement the high protein feed with scratch grains if you're unable to free-range.
If you use 20% chick feed, make sure to get unmedicated for adults. That is for protecting chicks from coccidiosis as they gain immunity, which adult birds don't need.
Hope that helps!
