If I wanted to breed specific hens I have, how would I go about that?...are there people out there that will rent or loan out a rooster of specific breeds for that purpose or how is that normally handled?
People do not usually rent roosters.
People who are allowed to have roosters will usually raise one from a chick, or buy an adult one, but in either case they expect to just keep the rooster for quite a while. When they do not want the rooster any longer, they either sell him or butcher him (unless he already got killed by a predator or died of a disease or something like that).
For people who are not allowed to have a rooster, the most common solution is to buy chicks, or to buy fertile eggs and then hatch them.