If he starts, try to catch him and hold him firmly. Don't let him down if he struggles or let him peck you. Carry him around with you while you do chores or whatever. When he's given up struggling and gets calm, then you can let him down when you decide. Then chase him around the yard. This shows him you are dominant and not to be messed with. Do this every day, whenever you have a few minutes. Even if he's not trying to attack, grab him randomly, carry him around, and then start chasing him about. If he starts trying to mate with a hen, shove him off and chase him around. Shove him with your foot. Keep doing this till he gets the picture that YOU are dominant roo. You don't need to hurt him, just get a bit rough-housey. It's rooster speak. Bullies of any sort don't normally give up till they meet their match and part of a roo's job is to be a bully, pretty much.
If that doesn't work, give him a good dunk in a rain barrel after an attack.
If THAT doesn't work...well, a severely aggressive roo is dangerous, and can really maim you or a child. They are only good for a stew pot. If you can't do that to him, try to give him away and be responsible and let whoever takes him know that he's an aggressive roo so you don't send him off to hurt somebody else.
The good news is that the above tactics will probably work. So give them a try.