Hello! Welcome to byc!
Make sure to check out the learning center- there is tons of good info there!
Roosters can easily be kept with the flock, unless you are looking to do a specific breeding program. I let mine roam with the hens all the time. I keep roosters because they play an important role in my flock- they watch for and defend the hens from predators along with having fertile eggs for the next generation.
A healthy rooster will mate and fertilize eggs most of the year, once they are sexually mature. Occasionally during extreme weather or times of stress a roo may be temporary infertile. Dur ring the coldest months some of my eggs were infertile.
Fertile eggs are perfectly fine to eat! They won't start developing into baby chicks until a hen decides to sit on them for at least 3 days, or if they are incubated.
As for mounting/mating- a good rooster will dance for the hens and let the hens decide to mate. A hen will squat to show she is willing. Some hens are particular and wont mate some roosters. A young, aggressive or virile rooster may over mate favorite hens, or all the hens if the balance is off. Generally you want at last 6-8 hens per rooster. If the hens are showing signs of over mating you can put aprons on them or separate the roo.
Some breeds of roosters can be aggressive, and I have found in the past that roos that are overly babied as chicks generally will see people as competition and may attack. There are some ways to try and rehabilitate them, with varying degrees of success. I personally don't tolerate mean roosters. A good rooster isn't all that hard to find. They will call the hens to treats, gently mate, watch for predators, and are non- people aggressive.
If you do keep more than one rooster make sure you have enough space and hens for each to have their own territory and little harem.
Also roosters should not eat layer feed long term. It has too much calcium. Instead feed a grower or all flock and have oyster shell available free choice for the hens.