Why are your hens laying eggs on the roost?

This is unusual but I have seen it happen. Young pullets will often not understand the use of a nest. If your hens are young give them time. The most probable cause of this is rodents. Mice startle the hens and they feel safe up on the roost. They will lay an egg anywhere they happen to be under those circumstances. One way to encourage use of the nest is to put a plastic Easter egg or even a couple of Golf balls into the nest.