Hello-
If you have different breeds, and you want to sell hatching eggs from a particular breed, for example Barred Rock, then you will need to separate the breeds. Unless your breeds lay a specific egg color, you won't be able to tell the difference.
If you collect the eggs daily, then your customers that want to eat the eggs will not be able to tell if they are fertile or not. There is a tiny dot called a "bullseye" that is actually indication of a fertile egg. The dot is often hard to see and it's like a white shadow. (That's how it looks in my humble opinion.)
You could put a rooster and his hens in a specific area, then you can incubate those eggs at first to see if they are fertilized. Once things are going well, then you could sell some eggs.
With free ranging, I do believe a hen could avoid the rooster, and avoid mating, so I think the chances would be less if you continue to free range them.
I would suggest containing them in a coop/run for part of the day, and allowing them to free range each day until dusk. If you want to advertise hatching eggs of a specific breed, then you don't want to free range the hens and roosters of different breeds at the same time, because then you could have mixed breeds.
