As a very rough guideline, I would say a rooster eats about the same as a hen, and a banty (hen or rooster) eats about half what a standard sized hen does. That will not be perfect, but it means you can just count chickens plus half of banties, then divide by four to get pounds of food per day.First thing is to count the birds and multiply by .25, equal pounds of feed per day you should be feeding. I'd ignore roosters and banties unless you have a lot of them. Now you have a baseline to judge if you are spending too much money in feed per bird.
If we want to be completely accurate, we also have to account for some standard-sized hens needing more food than others. Big-bodies hens that are good layers will be the most obvious ones to need more feed. I don't know of any source with accurate numbers for large hens, or roosters, or bantams.