In my experience, I keep the chicks in a protected run until laying because of size. Free ranging sounds nice but, you must know it comes with daily risks. Like preditors. Hawks will pick them up, right in front of you.
I don't seem to have many problems will full sized girls. ( I don't have a Roo). But, remember they will disappear at any given time so, Don't cry when your count is minus 1 or 2. Because once the preditors take one, they'll be back for a well fed chicken.
Good luck and take the suggestions given about intregration. (Merge: your term).
Also, they are lil raptors and WILL tear up your garden or flowers and they may not necessarily stay in your yard. Just so your aware of these things. Good Luck.