If there are no hens around, they usually won't fight, because there is nothing to fight about. I have a friend who houses his 6 or 7 roosters, all different breeds, in one coop, without any hens. He has never seen evidence of them fighting.
I have been under the impression than bantam roosters are a little less aggressive and more tolerant of other roosters, as compared to standard sized roosters. My own experience tends to support this, but this is based on a pretty small sample size, so I cannot say it is fact. I currently have 2 bantam Brahmas from the same hatch, a little over a year old, who get along well with each other housed with a bunch of hens. One is dominant over the other and seems to "possess" most of the hens, while the submissive one "owns" just a few of them.
However, each will sneak mate the other's hens. When one catches the other mating "his" hen, he will not attack - he simply mates her himself immediately thereafter. It can look like gang rape and is probably not very pleasant for the hen, so for that reason I am constantly considering getting rid of one rooster. Also, just because they get along well now, doesn't mean they won't suddenly start fighting one day....Like maybe when the dominant one gets sick or something, and the other one thinks he can defeat him.
I have another friend with 2 dutch bantam roosters, also housed with a bunch of hens. She has had them for years and they never fight. One seems to accept the submissive role and, as far as my friend knows, never mates any of the hens.
And, of course, the more space they have, the more likely they will be to tolerate each other. I think if they are always confined to a small space with a bunch of hens, they are more likely to fight. If the flock free ranges all day, the roosters are more able to avoid a nasty conflict.
Certain breeds seem to have a reputation of being more mellow and tolerant than others, with the game breeds obviously the more belligerent. Brahmas, cochins, and dutch are sometimes rumored to be among the more mellow. However, there seems to be a lot of variation within a breed (at least in my own experience), so I wouldn't hang my hat on any of that. If you confine 2 or more roosters (any breed, any size) with hens, you take your chances.
