Why do you want roosters? The only reason you need a rooster I if you want fertile eggs. Everything else is purely personal preference. What do you hope to gain by having roosters?
1 rooster per 10 hens is the most often quoted magic ratio for full sized chickens, 1 to 12 or 15 is more often quoted for bantams. But there is nothing magical about any hen to rooster ratio. Some breeders keep 1 rooster with 1 or 2 hens through the entire breeding season, they are called breeding duos or breeding trios and typically don’t have problems. Many people keep one rooster with over 20 hens and have problems with overbred or barebacked hens. Usually the eggs are fertile with a 1 to 20 ratio. The hen to rooster ratio has nothing to do with whether or not roosters fight. They are just as likely to fight with 1 hen as they are with 20.
Part of the answer may depend on how much room you have. When they mature roosters often split up with each claiming a certain territory and a specific harem. The less room you have the more likely you will see problems with multiple roosters.