Yeah, people have been keeping multiple roosters with flocks for thousands of years. Occasionally there are serious problems but it usually works out. Some have already been mentioned but I think some critical things are breed, space, the personalities of the individuals involved (both hens and roosters), and whether they were raised together, either as siblings or as father-son.
I recommend you keep as few roosters as you can to meet your goals but there are no magic ratios involved. We all have our unique situations so we’ll get different results. I’ve had more problems with good ratios than with bad. Each flock has its own dynamics.