Different people will give you different answers. I've tried quite a few suggestions...just because none worked for my roo doesn't mean it won't work for yours.
First off...do NOT act scared. He'll know. What you need to do is show him YOU are the dominant one. Next time he gets ya...or even LOOKS like he's gonna get ya...catch him. Push him down to the ground with both hands on his back, fingertips slightly wrapped around his sides. Do NOT let him get up. After about 30 seconds to a minute...slowly begin to release the pressure on his back. If he tries to get away, push him down again. Continue the cycle until this happens: You slowly release the pressure and he doesn't move. You remove your hands completely from his back, and he's still down...belly touching the ground. When this happens, he has submitted to you. It may only take one time, it may take multiple.
Another way to show him who's boss once you catch him: tuck him under your arm and walk around your yard. Parade him like this in front of his girls. They hate it.
A couple tips for you:
NEVER walk around him. If he is in your path, walk right through him. He'll move, and if he doesn't, it's because he's challenging you. That would be when you do the first thing...push him down to the ground.
Don't pet him. Hens groom the dominant male...petting him gives the impression that you are taking the roll of one of his girls lower in the pecking order than he is.
Now, worse comes to worse, smack him with a broom. I know lots of members here who have to walk around with a broom in their hands at all times due to aggressive roos. I wouldn't, personally, because I won't keep an aggressive roo.
Good luck, I hope he changes his ways for you!!