I have included pictures of Scarlett (a 15 week old Rhode Island Red). Scarlett was named in hopes that she was a hen but only time will tell. She was given to me from a friend who loves chickens as much as I do.
I thought that the spurs on the legs would be a good indicator of whether you had a rooster or a hen but I have learned that most all breeds of chickens have early spur knobs, hens included. See the picture of Scarlett's legs below and you will see the small pimple-like protrusion where a spur may or may not grow.