I always suggest you keep as few roosters as you can and still meet your goals. That’s not because you are guaranteed to have problems with more roosters, but you are more likely to have problems the more roosters you have. I don’t know what your ultimate goals are, that’s up to you.
It’s very possible you could have any or all the problems the others mentioned. It’s also possible you see none of those things, though that would be pretty rare. To me the most critical items are how much space you have and the personality of the individual chickens. One thing that is almost certain to happen is that the cockerels should mature before the pullets. Since the cockerels are bigger and stronger plus the hormones are really pushing them, they can be quite aggressive toward the pullets, forcing them to mate. That’s not just about sex either, that’s a way of dominating the flock. Chicken society can be pretty complex. If you have plenty of room and the boys aren’t too aggressive that can be fairly nondramatic, but it really can be stressful.
There are several ways to go about it if you plan on keeping more than one. You can leave them all together and see how it goes. Have your Plan “B” ready so you can isolate the boys if you wish.
You can keep all the boys in a separate pen, away from the girls. Lots of people keep bachelor pads. Normally the cockerels get along reasonably well without a lot of fighting if there are no girls to fight over. They will still decide which is the top cockerel, the pullets will also determine who is top pullet, but the fighting is usually not too bad.
There is a big difference in pullets and cockerels versus hens and roosters. With adolescents the hormones are often running uncontrolled and maturity is really irregular. Some chickens just mature faster than others. Once the chickens, male and female, mature enough to understand their roles in the flock things normally become really peaceful. But until they reach that point there can be a lot of conflict. Not always, but there can be.
You can lock two up and leave one with the pullets. It’s possible one cockerel can totally stress out a flock of 21 pullets, but the odds of that are less than having three cockerels running with them together. People will sometimes quote magic numbers about hen to rooster ratios but there is nothing magical about them. You can have the same problems with one rooster and 21 hens as three roosters with the same hens. It’s just that your odds are better with fewer roosters.
You can keep the boys in their bachelor pad until the hens and roosters are mature, probably around one year of age, then let them mix. At that age the hens should be mature enough to accept the dominance of the roosters so that part should go pretty smoothly. The hens will probably squat for the roosters without being forced (though some chasing may be involved) and the roosters should have the worst of their hormones under control. It’s highly likely (practically guaranteed) that the roosters will fight some to determine which is flock master. It is possible there can be some fights to the death or that one gets seriously injured, but normally if they have sufficient room these fights evolve more into running away and chasing. They normally reach an accommodation where they work together to take care of the flock. That accommodation can take many forms. Often each rooster gets his on harem. They may intermingle some but usually each sub-flock has their own territory and they pretty much stay out of each other’s way.
They do have a tendency to fight each time a new rooster is introduced to the flock so try to minimize that as much as you can. Once they are introduced and have worked things out leave them alone if you can.
What works best for me is that I raise the chicks with the flock, pullets and cockerels. I do not isolate the cockerels unless I am going to butcher them. Yes, there is often excitement down there when they go through puberty and adolescence, but I have plenty of space and they generally don’t get seriously injured. If you are not used to it, it is often not for the faint of heart to watch. I’ve never had a pullet injured. I had one cockerel kill another once in all the years I’ve been doing this. Only once and that is when I did isolate them. I had 18 cockerels so I put some in my grow-out pen and left some with the main flock. When I let them back together one cockerel killed another. If I had not isolated them that probably would not have happened. You are dealing with living animals so I can’t say for sure.
I don’t know what the right answer is for you. Your goals and set-up are different from mine. I wish you luck!
