Now, about roosters coming to your aid when another roo attacks you.... Yup. I have two little Silver Sebright roos in my flock, Alex and George. George is obnoxious and flogs any visitor he can sneak up behind. He has occasionally gone for my ankles and I have to walk him backwards to put him in his place.
However, he once went for a friend of mine and his brother, Alex, jumped at him and kicked his behind, chasing him away from her. Alex has also chased George after I have walked the little snot backwards a few feet until he gave up, then chased him for good measure.
My dominant roo, Carl, has also rushed in to bowl George over, right off his feet, when George snuck up behind me with his hackles raised in preparation for an attack. Carl is about six times (at least) larger than the Sebrights; George high-tails it across the yard so Carl can't catch him to do anything more serious to him.
Why do I keep George? Well, he's only 8 inches tall and IS an amusing little fellow.