Are they all the same age? If they are the one's with the most tail feathers could be your hens that is how I have be telling with my buff's last yr and this yr.
The roo combs should be coming in more but that is not always true either I have some hens with some big combs. I also would watch them walk to help. See which ones are more of a strut to there walk.
I've got 4 buffs 3 of which have short tail feathers and a more prominate comb. I am guessing these are all roosters. 1 of the buffs has longer tail feathers and a less prominate comb. This is what I am going by. Hope I'm wrong!