I'd give it a week and then try to integrate once more. See if he is seriously getting injured or merely run around and pecked whenever he approaches. I admit that free ranging allows for more freedom when it comes to integration but his breed, size or sex shouldn't matter one iota. He will learn to avoid the top roo and the hens will accept him given time.
I've integrated roos of different sources, chicks of different ages, hens from another place, etc. It all helps if they are given time to get used to each other before they actually can touch. They will still have to establish a pecking order but they shouldn't continue this after this had been established. It might also help if you separate him along with one of your more friendly hens and reintroduce them both back into the flock in about a week.