The insulation thickness must be at least as thick as the vertical slope else you will receive a warning.
How to make a slanted roof in revit.
In sketch mode select a roof boundary line that defines slope indicated by.
To create a sloped roof in revit modify the footprint sketch of the roof by selecting and specifying the slope defining edges of the roof.
By applying the defines slope property to lines of a roof boundary you can create different roof types including flat roofs gable roofs and hip roofs.
To specify roof pitch select a slope defining boundary line click the numeric slope definition.
The revit interface is a bit unclear about constructing a flat roof but no roof is truly flat and creating a flat roof in revit allows the designer to annotate the roof without having to deal with the issues associated with the modeled hips and valleys of a low slope roof.
When editing the roof sketch select the edge or edges you would like to slope and select defines slope on the options bar.
On the properties palette select or clear defines roof slope.
If slope is activated a triangle symbol will appear next to each boundary.
In the option bar make sure define slope is activated for boundary lines.
Want to create a sloped roof.
To create a gable roof 2 side slope remove slope for half the boundaries.
In the drawing area angle icons identify which lines of the sketch define slope.
To create a hip roof 4 side slope define slope for all boundaries.
Want a sloped structure or a sloped insulation in your flat roof.