Hello Mayur
Go to the Roof Specification Icon on the at the top of the main screen. Click on the second tab (Supported Cone Roof Data) and click on the little buttons with the 3 dots for:
1 Roof Plate Material (see help below), and,
2 Structural Member Allowable Design Stress
Select a material, and you should be good to go.
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Sincerely,
Ray Delaforce
CADWorx & Analysis Solutions
Hexagon PPM