I agree with being diplomatic but be careful about suggesting eating the roos. Find out first if they are pets. People who keep their chickens as pets can be very touchy about the suggestion of eating them. For people like that, suggesting they eat their roo would be like someone telling you to eat your dog or cat. It sounds like you are in a neighborhood, not in a farming type area. Your best bet may be to offer to help build a coop for the roos, although getting them to use a coop might be difficult since they are used to roosting in a tree. If you are lucky and they aren't pets then by all means, discuss eating them, but tread carefully. Try catching your neighbor when they are out in the yard. Remark about their chickens, something complimentary first. Strike up a discussion about the chicken fancy you share. Ask about the roosters, why so many? At this point if they mention eating them, go with it. If they are pets and there is no chance they are being processed, find an opening to mention the crowing (maybe something like "I never realized that roosters crowed so much, they can really keep you up at night, huh?"). See where that goes. Explain to them that you need more sleep and you would like to find a way to do that so everyone is happy. Offer advice on how they might be better kept quiet. Offer to help with the building of some appropriate housing for them.