I have 6 year old Easter Eggers, one being a roo and I put my 14, 6 week old pullets in with them. I first put them in a dog kennel when the adults were free ranging, all the hens came up one by one and looked at them for a second, and went back to eating. The rooster came up, looked at them and walked away. A few days later, I fenced off part of the run with chicken wire and put a few roosts in with their lamps. Again the hens and rooster went to incestigate, and didn't seem bothered and went back to what they were doing. They've been in the run for with the adults, separated, for a week now and there's been no trouble. The rooster even got in there with the pullets, he was only interested in their food though.
I guess it really depends on temperament of the chickens but mine did really well.