When you have a flock of male chickens, they will still fight even though they do not have access to the females, because they are still able to see and hear the females and therefore they feel as if fighting for mating rights is still needed. Do not always expect things to go as planned with a flock of males and have a backup pen. I have a pen of cockerels I still need to rehome but I had to remove two cockerels they were really beating up badly and I put them in a different pen, and they are doing just fine. The two cockerels do fight when they are trying to get to a hen on the other side, but other than that, they do not bother each other. Another factor to consider is that it is not the best idea to put bantam roosters with large fowl roosters, or a weak breed with a strong breed in general, when you are making a rooster flock that still is able to see and/or hear the hens. That would make for some severe injuries to the bantam roosters, or even death, if a big fight broke out. Just be careful and have a backup plan.