I don't know if this is helpful at all, but I've noticed that my "head rooster" keeps the peace.
If any of the hens (or one of the other two roosters) squawks because it is getting pecked on, he'll run over and put an end to the dispute. The flock does have its pecking order, but Spider Catcher keeps an eye on it. I have a frizzle bantam pullet that is in the pen and the older RIR hens will mercilessly peck at her if he is not around, but if she yells just right, he will "rescue" her and the hens will leave her alone.
So, yes, it may be that your roosters were keeping the girls in line.
Just a thought... I could be wrong though.
I introduced a new hen (Balli) to my flock not too long ago. Of course there was the usual sparring that they have to do to estabilsh the pecking order, but Spider Catcher seemed to keep a close eye on it and if Balli got too aggressive he would jump in and pull her off of whoever she was going at. As soon as she would "learn her place" he would leave her alone.... until the next time. Interestingly enough, though, if one of "his" girls started messing with Balli, he would watch, but not intervene. It was almost as if he was making sure she was on the bottom of the pecking order... where she still is.
Those chickens are *way* smarter than I ever knew. LOL
Good luck! I hope you don't have to keep them separated for too long!