Do you want your hens as pets, to be petted and held? Or do you just want to watch them sometimes, and get eggs to eat? If the former, do not get a rooster. If the later, a rooster can be of good help, but it is not instantaneous. They have to grow up, and they can be a bit trying until they do. If you have SMALL children, I HIGHLY recommend that you DO NOT GET A ROO. They can be dangerous, and small children move too fast and are scary to roos, who will attack them at eye level.
If you want chickens for eggs, well then, the same hens will not produce eggs for ever. You have to cull and replace. Now if you free range without a rooster, the wildlife will probably cull them for you. When I first started, I only had hens, and really a nice flock of hens is a good way to get started in the chicken hobby, however, I let mine out, and I frequently lost a hen, and did so right up to the time my roo got to be 14 months old, then the day time predation has stopped. It has to be my Captain.
Anyway, if you want hens for eggs, you really need to add a few pullets each year. You can of coarse, buy new chicks, and raise them up yourself, and then introduce them to the flock, but by far the easiest way is to have a broody hen raise them up for you. She can hatch them out, right in the coop with the layers and roo. She will keep them separate until they are accepted. Works a treat.
I have had my current flock for 5 years. I started with all hens, one darling girl went broody, and put fertilized eggs under her that I got from another chicken lady. Some of those chicks were roos. I picked one, and processed the rest. I really like the one I have, but I have never picked him up, or petted him, I walk right into him, and make him move. He has never attacked me or mine, and I love having him. But honestly, there are nightmare stories on here. Some make great roos, and some do not.
Sum up advice - no you don't really need a roo, but you will lose some hens to predation if you free range, you can lose some to predation if your roo is not old enough, you can raise up your own chicks with a roo, and you have to plan to replace your hens about every 3 years or sooner to keep a stable egg production. Pullets will lay through the first winter, but hens generally take the winter months off unless you add a great deal of additional light. Roosters and little children are not a good combination.
This is a great hobby, that you can grow into, your flock will change with time, and you can get a rooster later if you want.
MrsK