I can only tell you what mine have done. I don't have enough experience to tell you that all chickens do this.
What I noticed is that there is a difference in how they look when they spar. The roos could make their neck feathers stand out straight and the neck feathers appeared longer so when the puffed them out their necks looked really big. The females sparred but backed down earlier where as the cockerals kept going and the females couldn't puff up so much.
It seemed like the cocks could make their feathers puff all the way up to their heads, too.
I will go out and watch them and let you know.
Oh yeah, the cockerals also did this thing when it was two roos sparring that I didn't notice the females doing. The would both lower their heads with neck extended and stare each other in the eye (stink-eye) and have a staring contest at some time during the match. The females didn't seem to do this.
Hope that helps and like I said this is just my experience.
I am wondering this also... I have three bantams about that age, and I have been told from the lovely people here @BYC that it looks like 2 are roos.
When it is time for bed the two roos seem to fight over the spot next to the alleged hen, I am wondering do they know who is who , like who is a boy and who is a girl, at this age or are they just silly little birds?