I free range quite often, and while a rooster is not a 100%, having one for me anyway, dramatically increases your odds, but the rooster needs to be an adult rooster, about a year old. Immature roos are interested in one thing and it ain't protecting the flock, older roosters are more responsible.
By the time a rooster is near a year old, generally speaking (kind of, sort of) one can tell if he is going to get human aggressive. Personally I think the best rooster you can get is the second or third rooster from someone elses flock. I have had good luck with those boys.
This time of year, it should be easy to pick of a rooster. I have found introducing a single rooster to a flock of hens, one of the easiest additions to make. With in days, my girls thought he was wonderful.
I have run flocks both ways, with and without a rooster. What I have found is a full grown rooster will dramatically reduce the losses to day time predators. Without a roo, I often would lose a bird a month or more. Losses can occur, but much less often.
Mrs K