Wow, we're a cynical bunch, aren't we? Or perhaps we're just realists. I wonder if the reason you saw mostly bantam roos at this place is because they're the only ones too small for them to bother processing.
I'm curious also about how they can manage to be a working ranch with a large flock of chickens who also take in other folks' unwanted roosters as a form of community service and not dispense with any birds that don't contribute to their production. Unless they're just letting them free-range & scratch up their own food until the next bag of feed gets donated.
To answer your question, you should look for how these birds are being housed & fed. Do they all have a place in a secure coop to spend each night? Or are they allowed to roost in the treetops and get picked off by predators? Are all the roosters given feed to meet most of their needs or just the producing hens?
I know it's tough to find a home for a rooster you cannot keep, especially if he's a nice handsome guy that you really like. But the reality is that since even with a mixed flock the ideal ratio is 1:10, and with many flocks kept with only hens, that there are job positions as flock husbands, breeders, & pets for about 10% of all roosters hatched. That leaves 90% of all roosters with their purpose on a plate. Look at all the posts for free roosters on the Buy/Sell/Trade board. Sometimes you can't even give them away, not even for food.
But really, there are worse things that can happen to a rooster than to nourish a grateful human family. Some folks just sell/give away their roos with a "don't ask/don't tell" policy. But I'd prefer to know if someone planned to process my roos, and look for people who would at least treat the bird humanely right up until the end, who knew what they were doing so the end would be quick & efficient. I always tell folks who want to give me their roosters what my intentions are for their birds. If this rancher plans to process your rooster he should at least be honest about it.