How do I install some roofs?

[Amnekian]

I tried both the roof zone and no roof zone tools but to no avail. What am I doing wrong?

[Nilly23]

You need to build a room then a roof will spawn over.

[StorymasterQ]

Also, ensure the room is actually closed off. You can use walls, natural rock (cave walls), and doors to complete a room.

[Coenmcj]

For a roof to form originally, All cells must be able to form and support a roof. so larger spaces (8+ away from walls?) cannot have a roof occur, without support walls in the centre.