Here are a couple of threads about people having multiple roosters so you get more than just my opinion. There is more detail in them than I'm likely to give too. It never hurts to hear different people's experiences. Chickens don't all act the same.
Number of roosters thread
https://www.backyardchickens.com/forum/viewtopic.php?id=219443
Managing multiple roosters
https://www.backyardchickens.com/forum/viewtopic.php?id=229968
And here is one that shows that you do not have to have 10 hens for every rooster to avoid bare backed hens.
Breeders managing roosters
https://www.backyardchickens.com/forum/viewtopic.php?id=250327
The hatcheries are pretty good about sexing their chicks, but you are very right. It is possible you could get a rooster or two. Out of fifteen I got that were supposed to be pullets, I got one rooster.
Will the males fight. Yes. Will it disrupt your flock or cause injury? Maybe. Will the males fight a lot? Maybe, but not necessarily. Many of us have multiple roosters in the same flock. Sometimes there is serious fighting and injury, but sometimes there is not. When roosters are raised in a flock, whether as brothers or in a father-son relationship, they often reach an accommodation and form a good partnership to take care of the flock. They definitely know which one is dominate and there will occasionally be skirmishes to reinforce that position. Sometimes this involves serious fighting but often it mainly involves one running away and the other chasing. Sometimes these fights are to the death, but not always. I cannot tell you what would happen in your flock. I do think your odds of having a relatively peaceful situation is improved it they have a lot of room to get away from each other.
Often, the flock will sort of split up. Each rooster may have his own harem and they usually go their own different ways. But they will still work together in an emergency and they will peacefully roost in the same coop. And don't be surprised if you hatch the eggs if you find that all roosters are at work fertilizing eggs in both harems. There is a lot that goes on behind the woodshed that the dominant rooster does not know about.
One risk when you have roosters is that you may get barebacked hens. This is where the rooster removes enough of the feathers from the hen that she is at risk of getting cut by his claws or spurs when he mates her. If she starts bleeding, the others may turn cannibalistic and kill her. This can happen no matter the ratio of your hens to roosters. Some posters have said they have three roosters with two hens and this does not happen. Some have reported this problem with one rooster and 18 to 20 hens. That third thread above addresses this. The more roosters you have, the more likely this is to be a problem, but there is no magic ratio that avoids this problem.
Some people will quote a 10 hen for every rooster ratio. This 10 to 1 ratio is about fertility, not barebacked hens or roosters fighting. With a large flock, if you keep 1 rooster for every 10 hens, all eggs have a real good chance of being fertile. If you have more hens per rooster than this, fertility may decline. One rooster can usually keep more than 10 hens fertile, but the commercial operations use this 10 to 1 ratio for fertility purposes.
My usual advice is to keep as few roosters as you can and still meet your goals. Having roosters does not guarantee you will have a problem, but the more you have, the more likely you are to have a problem.
