It's very possible a rooster will kill a hen if you don't do something about their aggressive behavior, yes. It happens a lot more due to over-mating than pure aggression, but it happens.

Is it normal for a rooster to attack a hen?

A: Unless your rooster is causing the hens injury, pecking hens on their backs and heads is actually no cause for concern. It is courting behavior. He pecks them on their backs or heads as a signal that he would like to mate.

Will a rooster eat a hen?

There are many benefits to adding a rooster to the flock. Roosters are good protectors and can earn their keep when you have a large area in which your hens free-range. Roosters will also seek out and alert hens of the best food finds and tasty treats.