You can let then free range together as long as you have sufficient space. That changes the dynamics though. I’d still keep the pullets separate from the roosters until several of the pullets are laying. When you put the two roosters with the pullets, the two roosters will probably fight to determine which is to be flock master. How bad will his fight be? Who knows, certainly not me. It may go so smoothly you never even notice. It may be a fight to the death especially if one gets injured or if space is tight.
What will normally happen, especially if the two roosters were previously being housed together, is the two will face off and probably fight some, but one fairly quickly determines that they are better off running away instead of fighting. There will be some chasing and maybe a rematch or two, but they soon learn to get along. I’m going to keep mentioning space. It is important that the loser has enough room to run away and get away from the winner.
Once they have determined who is boss, each rooster will probably collect his own harem. You won’t have any say in that, the hens will decide which rooster they want to go with. The winner does not always get the most hens either. And just because there are two harems don’t assume the hens will be fertilized by that rooster. Neither hens not roosters put much faith in marriage vows. There is often a lot of hanky panky going on. It is also possible some hens will not go with any specific rooster but will form an all-hen flock. Flock dynamics can be really complicated.
The different flocks may at times mingle without any problems, but often the roosters keep their flocks well away from the other rooster. Here is that space thing again. If the two roosters are forced to stay in each other’s area because there is not enough room to get away, there is a greater chance of conflict and more fighting. They may be able to co-exist in a smaller area but your risks go up.
The two roosters and the hens should be able to share one coop. It needs to be fair sized and don’t leave them locked in there for a long time after they wake up in the morning, but they will probably be OK together. You can try to have two separate coops and have each rooster use his own coop, but don’t be surprised if they don’t go along with your plan.
If you want to control which rooster fertilizes specific hens, you can lock them together. It takes about three weeks or more for that rooster to be the for sure father of any chicks that hatch, so wait for at least three weeks before you collect any hatching eggs. When you combine the chickens again after separating the roosters, the two will probably fight again to reestablish which is flock master. People do that all the time and it generally works out OK, but there is another chance for one of them to get hurt.
