I had and lost one rooster to this. Crusty yellow spots started on comb and then gradually spread to the rest of the body and caused feather loss, an atrocious smell, appetite loss, huddling. This little guy, a modern game bantam cockerel, the crusty yellow spots are confined to his comb and face right now, but are spreading fast!!! Please help!!! He's a pet
I don't know much about diseases but from pictures I've seen your rooster has dry fowl pox, this link might help you. https://www.backyardchickens.com/t/690442/is-this-fowl-pox
Your rooster has fowl pox, which is a viral disease. It is spread by mosquitoes and other flying insects, generally. Being a virus, there is not cure; the disease runs its course in three weeks or so. If you have any other birds, I'd isolate the infected one. It would also be a good idea to treat the chicken area for flies and mosquitoes, to reduce the spread of the disease. Keep the infected bird/birds isolated, so that the disease spreads slower. Fowl Pox is not usually deadly, especially when it is dry pox, which your bird appears to have. If the scabs get larger and obstruct his sight (or just to make him more comfortable), put petroleum jelly on the scabs. This will soften them so that you can peel them off and he can see to eat and drink. You might also want to mix in some sulphur, which repels insects. Though not immediately likely, he may get a secondary bacterial infection due to the stress. To be safe, I'd get some Oxytetracyline like Duramycin or Tetroxy HCA-280 to treat him with. Hope this helps! Good luck with your little cockerel!