In your roof mesh node, create and attach this selector so that the roof meshes don’t spawn where a stair is present (Create a blueprint derived from GridDungeonSelectorLogic and override the function SelectNode like this)
This will create holes where stairs are. Create a new mesh like this and attach it to the stair marker and move it up so they cover all the regions properly
watch?v=OR1bw9ucz0w
In the future updates, I’ll emit Ceiling and StairCeiling markers as part of the builder itself so you don’t have to do this extra step