Roosters have nothing to do with egg-laying.
Hens lay eggs no matter what. If a hen doesn't mate with a rooster then the egg will just be an egg, and could never possibly be a baby chick. If a rooster mates with the hen, the egg the hen lays can be incubated or sat on, and it will hatch. Only when a rooster mates with a hen is there a baby chick in the egg the hen lays. Yes, the eggs that you buy at the store are not usually fertilized.