21 roosters and cockerels? Their both the same. If you mean 7 roosters to hens, then you might wanna make sure none are getting beat up, that sounds like a lot for 21 hens. I find 4 can be a good max for that many, im not saying yours are mean, just make sure they arent beating them up. Thats a bit of a high ratio in my opinionI have 21 roosters, & 7 cockerels.