The sperm of a rooster can live in the ovary for 14 days. Heavy breed roosters can have 8 hens, light breed roosters can have 10 hens. A rooster must be 1 year old before he impregnate the hens. Young roosters will impregnate earlier in spring then the older ones. When there are more roosters in a group only one of them will crow, this one is the boss.
Some breeds have agressive roosters, others have roosters who are just kind.
At the birth of a hen there's already defined how many eggs she will lay. The number of hour's daylight is also involved, therefore in spring the hens will lay more eggs then during the winter. You can create more light hours in the winter and then the hen will lay eggs very well, but she's faster through her number of eggs. From the age of 5 months a hen will lay eggs. Bantams lay smaller eggs.