Never approach a feisty rooster with any nervousness or trepidation. Walk confidently, and be confident in his space always. If he mates in front of you, knock him off of the hen.
If he remains feisty ... grab him by the drumsticks and hold him upside down until he is calm. Keep holding him upside down for 15 minutes or more in front of the whole flock. After this, assuming he remains calm, hold him upright (keep a solid grip on his thighs in case he gets any ideas) and cradle him. Offer him treats and keep holding him for another fifteen minutes or more. If he remains calm, release him gently back to the flock.
If all of this fails ... a solid kick or three applied as often as needed. Kick him solid, aim for the breast area. The goal is NOT to INJURE him! The goal is to 'best' him and make sure he is aware that he can not win the challenge. A feisty roo may require several such solid kicks, knocking him back a few feet each time, until he gets the message. Repeat as needed.