it is a privilege to be able to have and own animals in the way you have, not all of us will be lucky enough to never encounter a hard situation in this scenario id cull the rooster he is sick, suffering, and rehoming him will not come easily additionally there's a possibility he will infect someone else's flock or will be passed to another person only to receive inadequate care for his condition resulting in prolonged pain that could have been avoided. you are not a bad person for culling this animal, all life is precious and a bird can be just as loving and significant as a dog that being said opportunities are not the same for roosters and as a farmer and a pet owner it is your job to make a call that is best for your any animal in your care, we euthanize dogs who are in declining states of pain just the same as we would euthanize a bird