I let mine out only when I am home to keep an eye on them, but if I need to leave, a plastic bowl with Cheerio's in it usually gets them back in their pen with no problems. I usually do my chicken call "here chick chick chick" while shaking the bowl around, the roo's come running like mad birds and then the hens come right behind them. Occasionally I have a straggler who can be coaxed in with some one on one time.
Cheerio's = chicken magic!! I can get mine to do almost anything with just a few Cheerio's!
Hope this helps!