Actually, breeding your own meat bird is doable. I breed them small-scale for local chick sales. It's simple and difficult at the same time. The simple part is that I just use Cornish/Rock roosters and White Rock hens. The tricky part is the management of the breeders. Their feed has to be carefully controlled, and the hens MUST have saddles (I use a special kind of duct tape). The resulting chicks are technically Cornish/Rock/Rock, so the Cornish is just a little more diluted. They grow just a little bit slower than typical hatchery broilers, but it's not really a big noticeable difference - maybe an extra week to butchering weight. Personally, I believe they are a bit healthier though. I don't seem to get as many leg or heart problems with them.
For my breeding stock, I use Hoffman Hatchery, but I would assume you can use any hatchery broilers that are relatively healthy, and any large White Rocks.