The Limestone Roof is a slanted building-block covered with white roof-tiles on the topside having grey borders that you can use as a roof-tile or for other purposes (it can be rotated).
It can be crafted in your Crafting Menu (default key "Q"), but only after the crafting-recipe has been unlocked by
- crafting Stone Roofs
- crafting (blocks of) Bedrock Walls from Bedrock mined from the Fossil layer with at least a Stone Mining Cell, and
- crafting Limestone Walls from Limestone mined from the Fossil layer, with at least a Stone Mining Cell
To craft 8 (blocks of) Limestone Roofs at a time, you'll need (as of R43 in May 2017):
- 2 Stone Slabs made of Stone, Limestone or Bedrock in a Processor
- 4 (blocks of) Limestone mined from the Fossil layer, which requires at least a Stone Mining Cell to be equipped
- 1x Melted Wax made of Beeswax in a Forge or looted from Wood Treasure Chests or Stone Treasure Chests
Since R42 in May 2017 inner and outer corners blocks can be created for Limestone Roofs by putting them into a Processor. No crafting recipes are required for this.