I offer both layer food and game bird maintenance food (which doesn't have all the calcium the layer food has and that roos don't need). If hens choose to eat the game bird maintenance they can supplement with oyster shell, available 24/7. They always seem to know how much they need.
There have been articles indicating that layer food has too much calcium for roos, with kidney problems a documented effect (I think Diana - dlhunicorn - has some interesting references). My roo BJ was being cared for by someone else for some months while I was tending to my sick mom in the hospital. They took shortcuts and only supplied layer food despite promises to feed as I requested (I supplied the food) and eventually shared this info with me. For a time afterward BJ showed signs of gout (a side effect of messed up kidneys). His feet and legs seemed to hurt a lot, maybe not something others would notice but I knew him so well and could see the change in him. I employed a remedy for gout (cherries) and in time he got better. Back on the game bird maintenance food, there hasn't been a reoccurrence of his foot/leg problems. I'm not certain the problem was from having access strictly to layer food but I am suspicious it might have been. This said, it could be that BJ's body just couldn't tolerate calcium as well as another roos might. Most documentation seems to indicate that any kidney damage would not be reversible.
I suspect the reason there isn't much in the way of food out there specifically tailored to roos is that most folks less enamored with their roos than BYCers wouldn't buy a 50 pound bag for their one or two roos since most of it would go bad before it got used. And in the commercial world, little roos-in-waiting are generally killed while still chicklets. So the adult roo/hen ratio in the US anyway, is something on the order of 90 gazillion hens for every roo! Not much of a market.
JJ
Edited just to add that my feathered friends also get a myriad of other foods like sunflower seeds, fruits, veggies etc, oats etc, adding variety and interest beyond the commercially prepared stuff and thus also diluting the calcium take. It still fascinates me to this day that I've never seen a roo give oyster shell a passing glance yet the hens aim straight for it when they feel the need!