Believe it or not, I have found the bigger the rooster, the less aggressive he is. I have bantams that are vicious and seem to suffer from the napoleon syndrome.
I have a few Rhode Island reds that look at me as walk through he flock like "Geeze, do I have to move again?" and I even have one that will eat out of the kids hands.
Years ago I had a jersey giant rooster who was so relaxed, people used to pick him up and carry him around.
That being said, remember, there is always an exception to every rule! If that 10 pound giant had decided he was going to be mean, he would have done some serious damage to anyone he decided he did not like.
I do not know the opinion of people here on the forum and if I offend anyone I apologize in advance, but I do not like to take chances with people getting hurt when they are visiting the barnyard. I clip the spurs of my roosters, with-in reason. I know some people have talked about covering the spurs.
I have a splash orp roo and a birchen Maran roo and I only have 6 hens but I love them both, once in awhile they do a stare down but nothing ever comes of it. they are both huge and sweet. I was so glad they got along becouse I really did not want to eat either one of them. They even will dust bath in the same hole together, its really to cute.
RIR roos have a reputation for being mean, but I see on BYC that some people have nice ones. The meanest roo I ever had was a RIR. For sure it will depend on the individual. I don't think there is such a thing as a breed of roo that is 100% nice. (Or if there is, I'd sure like to know which.) My BA roo and my 3 DB Leghorn roos were standoffish but not mean, and they were Ideal chicks. BA's and BO's are supposed to be on the gentle side.
I wonder if they are more likely to be mean if they are hatchery chicks instead of from a good breeder?
My buff chantecler roo, sold just last week, was a total marshmallow. He let my whackadoodle campine hen pull out all his tail feathers, he never once even looked at me or the kids the least bit funny, and you could basically walk right over to him and pick him up and he was just like 'oh, look, you are picking me up, oh well'.
However that is probably individual temperament as much as anything and I am not saying Oh you must go out and get a buff chantecler roo
As far as I can tell from extensive discussions here, there IS no breed with DEPENDABLY quiet/unagressive roosters, although it happens more often in some breeds than in others. If temperament is really important to you, it might be worth the risks of buying an adult bird so that you could (hopefully) pick one with a proven track record of behaving the way you want.
A lot depends on who you want the rooster to be passive too. I have OEGB that are downright mean even to birds much larger than them. But they love human attention, and love to be held. My american game is not so friendly but actually is more tolerent of other roos as long as they stay away from his girls. By far the most passive roosters I have are the BRs they love to be held seldom challenge other birds and will follow you around like lost puppies.