They can be crafted in your Crafting Menu (default key "Q") after the recipe has been unlocked upon buying it.
They are light grey bricks with red diamond-shaped tiles.
To craft a set of 8 Medieval Roof blocks, you will need
- 1 stone
- 1 piece of wood
- 1 melted wax (either created in the forge or found in chests)
- 2 stone rods (crafted in the processor)
The roof blocks can be rotated by pressing and holding R and moving the mouse while holding the left mouse button.