The roof is laid out with individual elements on the roof sample.
For convenience, Pivot models are configured to place them on the roof frame with Vertex binding.
A metal sheet has a substrate, in edit poly it is enough to hide the roof geometry, leaving only the substrate (Plane), and lay out sheets as Instance along the perimeter of the roof, if necessary, apply the slice modifier to the group of selected elements, then make Unhide All in edit poly.
The archive version for Corona and Vray.
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