I don't know if a rooster will help much. Sure he could teach them to be more observant but you have to get a good rooster for that. I've had one rooster, out of the many I've owned, that would alarm when he saw a predator. He only made sure they knew of the danger, and could hide. And he didn't help much or even make a sound when a fox attacked in the middle of the day... Anyways you can go that route but you have to make sure you get the right rooster. But there are ways to keep snakes out.