Looks like injury to me. My roos have them all the time. Does he get in fights? I usually apply a dab of antibiotic ointment ( not the pain relief one) and withing a few days the scab will flick off and there will be a lighter color of the comb in the spot. After another few days it will even back out. Fowl pox is another concern but his eyes look clear and those don't look yellow and crusty. My bet is on injury from another roo or bird, maybe if he's foraging in brush or something.I noticed these scabs on my roo’s comb a few weeks ago thinking they would go away. They don’t appear to be going away, any idea what they are and how he may have got them?