I hen raise, brooder rear and hand raise roosters. Hand-reared I do for purpose of close and frequent handling as adults. The handling is done under a range of conditions and handled birds are expected to come into close contact with people they do not know. My roosters are not aggressive as adults and we have had some that exceeded a decade in age. Agression did not increase with age.
Some breifly become aggressive as subadults but I do not respond. They can peck or flog but I ignore and allow them to do it more if they like. If aggressor stops attack but still acts aggressive, then I move closer to enable more attacks which he quickly tires of. I am thick skinned and such birds are generally far from what they are capable of as adults so no damage to me occurs. I do not attack or recoil from them.
Adult roosters can be made aggressive if hen or chicks of their harem are threatened. That I see as good but also try not to threaten such groups, at least not during daylight.
Their can be a seasonal component associated with molt. Roosters in heavy molt tend to be defensive. Give them space since they feel vulnerable.
At least one breed for me is prone to man-fight when used as a breeder under commercial hatching egg production conditions. California greys are breeding machines and roosters of such are incompetent fighters but they still try. Owing to no interest in handling them I made no efforts to break aggression. Simply having a gamerooster around kept such stinkers in line.
