Some roosters are plain aggressive, but some roosters can learn to back down.
Be assertive. This does not mean "be mean". But be confident and in charge.
This is a post by Beekissed from another thread; she has more experience than most of us and is very practical minded. She has given lots of good advice on roosters; this is one of those posts.
"You can train a roo just like you train a dog. When you want a dog to do something you reward him when he makes a move toward the positive and provide a negative response for any misbehaviors. When your roo approaches you boldly, like you are nothing to fear, you need to get into his personal space in a confident way until he moves away.
The first time you advance, he will walk away from you...and you relent. He has learned that moving away from you is a positive move. If he gets used to you in his personal space you may have to push it further by walking towards him quickly until he moves away from you quickly....not chasing him, just merely teaching him that you will stop only when he gets far enough out of your personal space.
Do this at odd moments when you visit the chicken yard. Sometimes I startle a roo when he least expects it, just to keep him wary of me. You don't want him running for the high hills when you come but you do want him looking over his shoulder instead of vice versa.
It is important to walk with confidence in everything you do and keep your roo in the corner of your eye. As with any male livestock, it is always smart to be vigilant...this does not mean you have to always feel paranoid and looking over your shoulder. Just vigilant...the same as when you deal with horses, bulls, billy goats, boars, etc. They have the hormonal and instinctual drives that can make them unpredictable at any given moment~ a smart farmer knows this and always remains vigilant to this.
A roo that is already been getting away with unacceptable behavior needs similar training but will require a little more assertive moves to break the cycle he has gotten into."
I can't find another detailed post that I remember reading. She carried a stick and would tap (not hit) him on the back to get the rooster to move around. It was like it was an extension of her, to increase her "size" and to get the rooster to respect that she could make him move around at her will. Not vice versa. If I remember right, she would also walk around the chicken coop/yard and if the rooster wanted to go somewhere she might move him away from it and keep him away for a little bit. Just to confidently show him that she was in charge.
Again, not mean, just with intention.
Some other people have recommended picking up the rooster and carrying him under your arm while you do chores, etc. Nothing says "I'm not in control" like being hauled around at another's will. I'm not sure I could do that though if the rooster was to the point where he'd physically hurt me though.
I hope you get some advice you feel comfortable in trying, and that works!
