Hawks

Unfortunately, one of the biggest problems with having free roaming chickens are hawks. They are sneaky, patient, and fast. I've let my chickens free roam my backyard for almost 5 years before one day, a new hawk comes to the neighborhood, and quickly, within a week, kills 4 out of my six hens. They swoop down, pin the chicken down, and tear it apart. And the only way for this to not happen is prevention, not treatment (like shooting it) because hawks are protected-at least in a neighborhood. I tried putting up those shiny garden streamers in the trees to confuse it, didn't work. Keep them close to people and the house, didn't work. Only let them out when someone is watching them, didn't work. (A dog protecting the flock probably would work but me and my dog weren't there). Now I have two hens left that were too scared to even come out of the coop, so I took them to the farm I am staying at right now. Where they can be in a new place with more chickens, and hopefully forget about their horrible experience.
So if you want your chickens to be free roaming, then it would be good to make sure they have lots of low cover places to hide in quickly. Or put up a lot of netting over where they like to go. And probably only let them out when you are around would be good, too. I've heard guinea fowl are great for scaring off any kind of intruder because they become very noisy and freak out. Whereas chickens usually become quiet when in danger, not guineas, and probably turkeys or geese might make good guard dogs....Otherwise, if you can't get rid of your predator problem, then it would be safest to keep them in a confined area. Or you can let your chickens be free roaming and happiest, but with a very likely chance of getting killed. But even with my hawk experiences, I would still let my chickens free roam. Unless of course the predator refuses to leave, then I'd have to confine them, or take them somewhere else, like I did.