By Battery Hens I assume you are talking about commercial raised layers. They would most likely not be familiar with a roost having lived in a tiny cage so far. I would think a roost would be a benefit to them but don't expect them to take to it right away, they will have to figure out what that stick is for before they start to use it as intended.
Most of the birds I've seen in commercial settings, do not have the luxury of any of the things we, as chicken keepers, think of as normal. A laying bird is used for around two years at most before being dispatched for a new crop of layers. These birds barely have enough room in their cage to sit upright much less move around or roost on a true roost. Like fryers, they are raised for one purpose only, to lay eggs. When they slow down they are replaced as fast as possible so the eggs keep on rolling down the chute.
