I noticed that when i build a comms console or a stove first, then surround it by walls and a door i get a structure with no roof.
I noticed this on two occasions when the stove and the comms short circuited in The rain. The situation was the same in both cases where i build the device before the building.
Anyone notice something similar.
Have you built a door in the opening used to allow colonists access to the room? Once you build the door it should complete the roof.
Also, check to make sure there isn't a no roof zone over it. I know it sounds dumb, but it has happened to me so I figure there might be another who would fall for that self laid trap.
It was the door me thinks....