What is a simple roof definition?

Roof definition refers to all the elements covering the building: 
- the roofing materials (clay tiles, metal sheets, Bardoline shingles, bitumen corrugated sheets Onduline HR, Onduline Zigana, Onduline Zigana Tiles, Onduvilla tiles) 
- the wooden or metal structure that supports them, made of the intermediate purlins, rafters and battens.