Is he the dominate rooster? If yes, don't. If not are you going to put adult hens in there also? He may try to breed with the younger ones and cause damage unless he has adults with him. To be 100% honest, I would not put him in with them until they are of laying age. It may work if you do, but the damage he could cause does not out weigh the benefit.
If your two roosters just fight but no one is getting seriously hurt, that is much better than him killing the chicks. Just my 2 cents.