I've been free-ranging my birds for over 15 years, and now and then, there's a predator problem. But not usually. The worst have been dogs. A couple of times, my own, until I got them trained properly.
I think folks over estimate just how much protection a roo is for a flock. Even the meanest roo is no match for a fast fox. Don't think your hens are safe because you have a rooster, they're not. Roos mostly protect hens from other roos, the family dog, house cats, (who seldom bother chickens anyway) and small children.
If you have white birds, they're more likely to be spotted by a predator. Other colors do a lot better. Bright gold birds, like buff Orpingtons, also stand out a lot. Not quite as bad as white. We started with an equal number of BO's and black Australorps, and s few various other colors and breeds, but after 2 "year of the fox" seasons, all but 1 BO was gone, but I still had a lot of black Australorps and assorted partridge and shades of buff/black/brown. No white, every single one I've tried to keep got grabbed by something.
Birds with their own natural camo are the best for free-ranging. Partridge and birchen, that sort of coloring. They blend.
The best protection for your birds is a good dog, but you have to work with them and make sure they will guard the birds and not kill them.