if his wattles and comb is injured, it's most likely from being pecked by other chickens..
do you have other roosters?
if not..it could be a predator..such as a weasel or raccoon, or cat..
what all are you feeding him?
what are his living conditions?
what bedding are you using?
does he have access to clean water?
is he underweight?
could he have been exposed to any dusts, or lawn/garden dusts?
describe his droppings..color and consistency.
check his throat and mouth for any sores.
check him for mites.
separate him to a safe place with food and water, and treat his wounds with diluted betadine and neosporin..
as long as he has blood on him..the other chickens will continue to peck him..even to death.
give him some extra protein..such as cooked egg, or canned cat food.
if you have poultry vitamins, give him them..or you can use Poly-vi-sol liquid baby vitamins, Enfamil brand..no iron..
give 2-3 drops on beak once a day for a week or so, then taper off for the next week.
he might need an antibiotic..
my preference is Tylan 50 injectable..
found at farm/feed/livestock stores in the livestock section.