From the Architecture tab of the top ribbon select the “Roof” tool drop down box and select “Roof by Footprint”.

Ensure the correct Roof Family is selected from the drop-down box at the top of the Properties Side Panel.

Model the Roof.

Adjust the Roof pitch by selecting one of the Roof Footprint Lines and unticking the “Define Slope” box in the top ribbon to remove pitch angle. Ticking this box and entering an angle into the field next to the line adjusts pitch angle.

Adjust Roof Elevation. This can be done in the Properties Side Panel or by moving them in an Elevation view.

After modelling the Roof outline Revit will ask “Would you like to attach highlighted Wall to Roof?” clicking “Attach” will trim Exterior Walls to the Roof.