What you see it the gray roof sheet as seen from the inside, with a fold in the middle to fuction as gutter. The two wooden strips have different functions: the right hand wooden batten is a modular part of the construction beam. It can be linked to the next module.
The left-hand batten is only part of the box-like structure. This box-structure gives some ridginess to the roof module.
The cross wide battens together with a sheet layer is part of the ceiling. It could be made from bamboo mesh covered with plaster.