To me this depends on your goals, management techniques, and facilities (especially how much room). The personalities of the individual chickens, male and female, also play a part.
Dad kept one rooster with 25 to 30 free ranging hens. Practically every egg we put under a broody hen hatched so good fertility. My laying/breeding flock is one rooster and between 6 to 8 hens, but during the season I may have more cockerels than pullets (about 45 chicks total) that I'm growing to butcher age, about 23 weeks for the cockerels. Maybe every 3 or 4 years it gets rowdy enough that I separate some cockerels but most years it's not a problem. They have a lot of room.