Provide them with a roost that's not too high, not too big or small, and not too slick then leave them alone. They'll know when they are ready to use it. Trying to make them use it will only cause more problems than it will solve.
I've had some flocks that were entirely on the roost at three weeks of age. Others still weren't all using one at three months of age. They all started to lay right when they were supposed to.
I've had some flocks that were entirely on the roost at three weeks of age. Others still weren't all using one at three months of age. They all started to lay right when they were supposed to.