I think you are just wonderful for taking in this guy! He probably will never realize just how lucky he was to land in YOUR yard, but we realize it!
We have a mixed flock of 20 or so hens. We have every size from tiny Japanese to big round cochins, even a Jersey Giant! This spring we rescued a mature rooster, and introduced him to our flock with great nervousness. He is the best thing to ever happen to our ladies! Dont worry about the size or breed of the hens. Rodney wont! Our Chesters favorite lady is one of the Japanese, and one of the Rhode Island Reds! Go figure. One is bigger than him, one is half his size. neither are his color!
Its true birds of a feather flock together, but roosters arent that picky!!
Dont worry about trying to coop him just yet. Go find some nice plump ladies (older would be better for him to begin with
) put them in the run, and watch how quickly he invites himself in, and then close the door. Or better yet, put him in with them at night if you can, while they are all quiet. But if he's still loose when you get the hens, they will catch him for you!
Then leave him in the run and coop for a few days. The ladies will show him where to roost, after about 3-4 days of this, you could let them free range, they will take themselves in at nightfall.
Good Luck! and enjoy all those tasty eggs!