I have two roosters, I love them both so much they are my pets. They are 21 weeks we have two other hens their age and have two more 11 week old hens I plan of integrating soon.
It is hard for me to talk about behaviors with chickens in that older age bracket and say that one thing is definitely going to happen. Real life doesn't work that way. If those older pullets are laying they should act like mature hens. The one on the roof she may be trying to get away from the boys, my guess is that she is not laying. The other one may be.
Your younger pullets should act like chicks until they start laying. There can always be exceptions but what that means in my flock is that the younger pullets avoid the older until about the time they start laying. I often have my 5-week-old chicks integrated with the flock of adults but what that means is that they stay away from the older ones during the day and do not sleep on the same roosts together at night. But the older do not go out of their way to harm the younger. I personally don't care where any of my chickens sleep as long as it is predator safe and not in the nests. Good luck on the integration. If you have sufficient room it probably won't be that rough.
I'm not one that automatically believes a cockerel is practically always a terror waiting to happen and will never be any good. As to the fighting, they are determining which one is the dominant one. It sounds like you know but they are still fighting. They could fight to the death. One could be seriously wounded during that fighting. Or they may reach an accommodation where one accepts the dominance of the other and they work together to take care of the flock.
The less space you have the more likely you are going to have a bad result. We've domesticated them so you can have exceptions but the natural instinct is like a feral flock. The dominant rooster runs any challengers out of his flock entirely so the flock can live in peace, very much like how in a wild horse herd the herd stallion runs any male challengers out of his herd or kills them so all the mares are his.
You can have exceptions, I have. Domestication has changed them some. But the basic instinct is for the dominant one to run the others out of his flock.
How will the boys treat those younger pullets? Again, lots of different things could happen. Usually in my flock they leave them alone until they start to lay. But usually doesn't mean always. The number you have may work against you. I often have three or four different aged immature chickens in my flock along with adults. The boys practically never bother the younger pullets but they have several their own age or older.
Should I get rid of one of my roosters?
I would. it's not that you are guaranteed problems keeping both but problems are much more likely if you keep both. Your stress level and the stress level in your flock will probably drop considerably if you do.
I would be rehoming my less dominant rooster who is not the leader of my current flock
It is possible either cockerel will become a great flock master once they get past their immature hormone-driven adolescence. It is possible either will become a terror as he matures, either human aggressive or hard on the hens. While they are immature adolescents they are often hard on the girls but that is not a good indication how they will be later when they all mature.
I cannot tell you how one will react when you remove the other. It is possible with the competition removed the one you keep will calm down. Or with the other gone they may feel free to become a terror toward you or the girls.
Good luck!