Your concern for the rooster is good of you. Your unfenced yard would not be safe for the bird--in addition to the possible traffic hazard, predators in the shape of neighborhood cats and dogs would endanger him.
It sounds like your neighbor took the rooster as a favor to a friend, not because she wanted him. May I suggest that you find someone who has a small flock of chickens and see if your neighbor would farm out the bird (yes, that was a pun and I'm sorry). Chickens are flock animals, and the rooster is probably lonely as well as bored. He could be introduced to an existing flock if there is no other rooster. Anyone who has kept chickens would know the procedure and would likely welcome a healthy rooster.
If you don't know where to look for a new home for Chanticleer, try asking at a feed store or call your local agricultural agent. Good luck!