We did that with Scout, sunflour. He was the little roo chick that suffered frostbite on his toes when he was just a couple of weeks old and had to be brought it for treatment. We had him in the house for about 3 weeks, but we took him out regularly for "supervised" visits with the flock and watched him carefully. The first time we had to bring him in, he was less than 24 hours old but he'd gotten out from under Mama Agatha and when I found him he looked totally dead. I brought him in, set up the brooder, and warmed him. Within a couple of hours we put him back under Agatha. She accepted him back and all was fine until he got his feet frozen at the waterer.
When we did the the supervised visits, we took him out to the run and set him down. The first couple of times, Agatha was glad to see him and took over where she left off, defending him, leading him to food, but she wouldn't cover him. We'd leave him out until he'd start picking up his feet and tucking them under him, then he came back in. We did this for a week or so - taking him out, daily,seeing that he was able to feed and drink, then leaving him alone with them mingling with the flock (with no help from Agatha). Once the Bigs had their curiosity satisfied and reminded him of his "boundaries" he was free to roam all over out there. Then we set his brooder up out in the coop with the door propped open just enough for him to get in and out. He was rarely in it, though. He was usually out in the run and the coop with all of the others. I do believe in supervised visits.