If you have quality rir then at a minimum you want one cockerel. You can work with that.
My 2013 pure rhodebar hatches averaged 70%. That worked out great as it gave me a lot of cockerels to choose from. I put many birds in the freezer and kept only 2 of each sex. I did NOT sell my culls as I believe the breed needs so much improvement that that would be inappropriate. I put more than 60 in the freezer. There are a lot of folks selling Rhodebars as eggs or chicks just because they have that breed and are not working towards improving it. This will devalue the breed and create a mess by lowering the standard. This is not a long established breed that has quality and consistency. The genetics are only valuable if they are an improvement on the previous generation. Keeping only the best ones to breed will improve the breed much quicker. Do not breed your third and fourth choice just to put more birds on the ground because what you will be producing will be inferior. No matter how many you hatch each year if you will cull hard and deep then that is the key to improvement. Too many people breed many of (or all) they have of a breed that is not yet consistent in type and quality and all they do is perpetuate the poor quality.
At what age do you butcher the cockerels, and what is the carcass weight? I'm not yet breeding them, but I might, and that answer is an important one for me. I have 11 eggs in the incubator now and only planned on keeping the pullets to maturity and then (perhaps) buying a cock/erel from someone local (though there is only one that I know about and not sure if he is a "breeder" or a "producer").