I don't have bantams, but I do keep multiple roos. I have 2 LF Cochin roos in with 18 hens(with 12 more in the brooder!). They get along pretty well. I do see them occasionally kick each other, but I've never notice any evidence of bloodshed. They each have their own little harem of ladies, and they take good care of them. My coop and run are pretty large though, so everyone has room to get away should a squabble start.