Sadly, I think as long as he has food on the premises and water in the pen, the animal control can't do much(or won't).
I think the best approach to this problem, is education. Explain that the chickens need a shelter, preferably some nest boxes, and he needs to get his rooster/hen ratio fixed. Also, it sounds like he may be over crowding the birds, explain to him that a few birds WELL taken care of, are always more valuable than a bunch of birds that are BARELY taken care of.
Suggest that he sell some extra roosters, and maybe some hens. I don't know how much space he has for birds, or food he has for them to eat. Explain that he will get more eggs by keeping "just" enough chickens that he can free feed at all times. Also, tell him that the metal roosts will most likely be too cold in winter, hate for him to lose birds to frostbitten feet.
If all else fails, plead to animal control to suggest he reduce his number, provide adequate feed, and provide proper roosts. They may not have to confiscate birds to set the owner straight, just scare him a little.