Go to the Roof floor and select Construction elements > Floor slabs. From the menu that appears press the Sloped roof button . Select the properties of the roof and introduce a closed perimeter corresponding to each roof slope.

Introduce the differences in elevation of the slopes using the Introduce elevation changes in roofs button . Bear in mind that these differences in elevation are defined with respect to the original level of the Roof floor (0 m since this floor cannot be assigned a height). Therefore, depending on the height that has been defined for the last floor, the elevation differences that are to be introduced will be different (see How is a sloped roof introduced?)

To introduce the façade of the mansard roof, click on Construction elements > Close elevation change and introduce a façade to close-off the existing elevation difference at the roof and, if required, a window.