All breeds can be sweet and they all can have issues. Find a breed that has a calm disposition. Orpingtons are laid back fluff balls. However any rooster can become a jerk with *play* activity that promotes aggression. For example, on the net is a video of a man who loves his cockerel. He plays feet tag and runs, lets the bird chase him all over the yard. He allows the cockerel to bite his shoes and laces even his pants. It makes the cockerel aggressive and eventually it will not be fun. He is training a young bird to be aggressive. Some young child is going to get hurt. The video promotes people to play games with birds. Its cute when they are baby's, it is not cute when they are adults. Good question. Good roosters happen with environment, selection, training. Good luck and enjoy your search! Read up on health management, exercises, feed, housing.