As for you question, leave the cockerels with the flock. The matriarchs of the flock will help to school them in the correct behavior for chicken society. What I would do, is keep a strict eye on the pullet chicks that you have coming up. The cockerels may get too rough with them. At that time, you might need to pull the cockerels from the flock for a while, and let the pullets grow up a bit.
Raising a rooster takes time, and as stated above, they really need to be nearly a year old. Another idea is to ask at the feed store, or your local poultry club, or county extension group. Often times people will have an extra rooster that is so nice, it has not been culled. These have usually been raised in a multi-generational flock. They tend to be very good roosters, and one knows by then how they will most likely act.
The best way to get a good rooster is a sharp knife, and anything that is not is invited to supper. Roosters are one place where you should not let your emotions guide your decisions. As AArt says, roosters are where romance meets reality.
Mrs K