In the drawing area angle icons identify which lines of the sketch define slope.
Revit make a flat roof.
You can also use toggle slope defining on only a few of the lines to create different roof profiles such as a gable.
Make sure you have selected roof by footprint from the drop down tools.
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.
Let s start off with a flat roof first.
Add a flat roof.
The second option in the list is toggle slope defining.
Select toggle slope defining for each line of the roof outline.
Attach interior walls to the roof.
This option turns off the roof slope extrusion for the line.
Add roof lines with a slope and an overhang defined.
Get this revit file here.
Select the lines of the roof outline and right click over the line.
When editing the roof sketch select the edge or edges you would like to slope and select defines slope on the options bar.
You need to make sure you are in a floor plan view in order to use the roof by footprint tool.
Go to the new level for the roof under floor plans on the project browser.
Your now have a flat roof.