First, click on the roof to open the properties panel on the left.

To change the base elevation of the roof, go to the dimensions menu in the left panel and enter the desired value into the Elevation field.

To change the material of the roofing, go to the Material drop-down menu in the panel. Either click on the upper drop-down menu to select a user-defined material, or select the upper Fetch from Store to open a carousel of various other materials. Select the desired material by clicking on it.

To change the material of the roof base, go to the Material drop-down menu in the panel. Either click on the lower drop-down menu to select a user-defined material, or select the lower Fetch from Store to open a carousel of various other materials. Select the desired material by clicking on it.

To delete roof, click on the targeted roof. Either press Delete, or select Delete Roof in the left panel.