The Square Roof Platforms Pack is part of the Castle Builder System. It is made of "Dwarvenite". This item was initially available as an add-on to a pledge level during the Castle Builder System Kickstarter. The item comes in both painted and unpainted versions.
The Square Roof Platforms Pack comes with these 8 pieces:
(4) 4x4 Roof Platform
(2) 4x8 Roof Platform
(2) 8x8 Roof Platform