I have a chicken, we thought was a rooster. It struts and grew spurs. One day I saw it lay an egg, i thought this can't be happening. Well the other day it was brooding, I scared it off the eggs it was sitting on. It went outside and proceeded to mount another hen and have sex. Later it was back sitting on eggs. Still not sure if it is male or female, but we named it - hesheit - just to be sure. It's very bizarre, don't think you are the only one. I was just goggling male/female chickens and only came up with a weird sight that has chickens that are literally half male and half female. That is not what is in my hen house :)
I'm pretty sure if you saw it lay an egg it is a hen.
I know that some hens can be overly aggressive and display rooster like behavior, but roosters don't lay eggs.