Balmoral, you are dealing with living animals, each with its own personality. None of us can give you any guarantees as to what will happen but we can give you some suggestions as to how to improve your odds of not having major problems. You can still have problems, you need to monitor the situation and possibly take steps. Since you are dealing with different living animals each situation is unique.
I don’t keep “bachelor pads” for fully grown mature roosters but I sometimes do with immature cockerels whose hormones are running wild. I’ve found that even with the pullets and the rest of the flock right next to them through a wire fence, things are normally pretty calm in that bachelor pad. Others have said they have to isolate the bachelor pad from hens and pullets to stop them from fighting. I certainly believe that what works for me might not work for others.
I don’t know how you have them now. Are they all ranging together or are they now isolated from each other? If they are all interacting with each other now, I would not expect a lot of serious fighting when you lock them up. There might be some, any change like that can disrupt the pecking/dominance order, but they’ve probably already worked most of that out. When you put roosters that are strangers to each other or add or remove roosters they have to determine the new order. That can lead to more serious fighting.
How serious will that fighting be? It depends on the individual personalities but room is also critical. Some roosters will fight to the death, but often one determines he is not going to win so he tries to run away. The winner will often chase him and sometimes there are more fights, but often if the loser can run away and get away they work out an accommodation. They know who is boss and they can live together. A flock of nothing but hens can react the same way. They have to sort out the pecking order so they can live together peacefully. It’s called integration. Sometimes it’s quite peaceful, sometimes it is really rough and dangerous.
I don’t know how you have your chickens housed now. I don’t know why you want to separate the roosters from the hens. If they are living peacefully now there is a good chance they will continue to live peacefully this winter, depending some on climate which might restrict room. By trying to separate out the roosters you may be creating problems where none exist. If it’s not broken, don’t fix it. But if you decide to separate out he roosters as large a bachelor pad as you can manage is probably your best bet. But have a plan B ready in case you need to isolate one or more roosters from the other bachelors.
Good luck!