Roosters are easy to come by. Sometimes people get stuck in a position that by random chance they got this bird, and that is their bird and they have to keep him. Not true. Let that bad boy go.
Go to your feed store, contact the county extension office, or a local poultry club. What you want is a rooster that is close to a year in age, raised in a multi-generational flock, and was raised up in an area with similar predators, and one that is so darn nice, that he didn't get culled by someone who would have culled him if he was mean.
Often times, a cockerel raised up with just flock mates, no older chickens, often times does become aggressive. I am not a believer in training them, they have a very small brain, and very large testicals.
Do remember that a emergency room is expensive, and let that boy go.
Mrs K