If they're locked up in the coop at night, you probably won't have to worry about owls. My neighbor lets her roosters roost in trees at night, and she suspects she lost at least one of them to an owl.
The calcium content of layer feed is generally too high for roosters, or for hens when they're not laying (e.g., during the molt). I recommend an all-flock feed (e.g., Purina Flock Raiser), but you'll have to provide crushed oyster shell in a separate dish for the hens. They'll take what they need of the oyster shell to meet their calcium needs.
Good info from previous posters. One bit of info I'd like to add: It's the flock owner's responsibility to see to it that their birds don't bother the neighbors. My birds will go visit the neighbor across the street, and he says he's happy to have them visit. He'll often stand in his driveway and crow at my roosters. But, his garden is not fenced, so when my birds wander into the road, I know it's time to bring them home. They can also wander into the woods behind their coop, which are owned by an other neighbor... again with his permission. He's happy to have my birds gleaning insects from his woods. But... if they go towards the next property line... time to call them home. You can train your birds to come to the verbal call from you accompanied by the sound of scratch rattling in a bucket.
