Many people are under the mistaken impression that you need to have roosters in order for your hens to lay eggs, but this is not so. However, in the absence of roosters, hens will step up and try to take on the role, but besides the obvious, they are unable to do so. Even so, dominant hens will mimic the behavior of roosters by mounting other hens. I have not seen hens share amongst each other; it is a free for all with the strongest, sneakiest, or swiftest, winning. When a hen finds a treat to eat it will make a certain noise which attracts other hens who attempt to steal the happy. As far as protection goes, it is also a free for all. Most hens are actually oblivious to the many potential dangers. I have seen hens happily running around or scratching the ground while hawks and eagles circle above. It is very rare to see hens look up for predators; ducks, well known for their rape culture can actually teach hens to look up, but this is normally the province of roosters.
When too many roosters are present, there is utter chaos. One year I briefly had around fifteen roosters with around sixty hens and it was a nightmare. First of all, the roosters fought among each other constantly. They do not crow only in the morning like in cartoons--they crow constantly, and they delighted in kicking each others' crows short. That was the only amusing thing about having so many roosters. Like hens, roosters will make a certain noise when they find a treat, but it is supposed to attract the hens and be shared. With too many roosters, the hens would first be attracted by the noise, but after so many gang bangs they lost trust; sadly a couple lost their lives as they were raped into the dust. All but one of the roosters were executed, but the damage was already done--most of the hens had no respect for the remaining rooster. Hens would get into fights with each other which the rooster was unable to break up. He would find a treat and call, but none would listen. He could still offer protection, but he could not fulfill his reproductive duty as he was often rebuffed.
After the above, it is quite a difference to see a rooster perform his duties properly. Things are certainly a lot more peaceful. This is not to say that everything is perfect, but given the three alternatives, this is most preferable. Protection is not always against foreign enemies, sometimes roosters must protect hens from each other. For various reasons hens will fight with each other, and can these fights turn deadly. Some hens can actually become outcasts; I have no idea what the causes are, but some can actually be kicked out of the coop and forced to roost outside at night. There were a couple hens I had that were just utterly despised by everyone else for reasons I could never discern. They were beautiful Silver Laced Wyandottes but they apparently must have committed some unforgivable crime and eventually died.