Your birds should go back into their coop at night as long as they have been there long enough to recognize it as their home, so about a week. I just leave my coop door open and they always go back inside an hour or so before sunset. What concerns me is the predators. For that reason, I would only let them outside when you are home and within seeing/hearing distance of them. Maybe let them out for a couple of hours at the end of the day and then you won't have to round them up if you need to leave; you can just shut the coop. A good investment would be to build an outdoor run that is connected to the coop so that they have enough space to mill around without being exposed. If they are in a small space 24/7 then you'll have issues with picking and boredom and whatnot, so depending on the size of your coop and how many birds there are, a run might be a good idea. I like to allow 3-4 square feet per bird for full size chickens. Good luck!
