Though not a Rock, my Delaware rooster has serviced as many as 25 hens successfully yet still has his favorites. It's not unusual for a Delaware to need more hens than the average LF rooster. However, my late Blue Orpington rooster, Suede, had as few as two hens and though he was not an overenthusiastic breeder, his sheer size necessitated saddles at one point for them because his nails just tore out feathers when he tried to balance. Generally, he did great with only 3-5 hens with no excess wear and tear on any of them, for most of his life. It just really varies by rooster. but I recall all my Rock roosters being somewhere between the two extremes.
What is that hunk in your avitar????