There are a number a ways to make roofs. And determining the best way is key. @ehsan can address the right way, but here is one way I made a Roof from face:
A roof from face has to be attached to a mass. A mass, per the SDK has to be made a family. So, here I create the mass in Rhino, then I create a Mass Family in Grasshopper named roofmass2.
Then get its Type and Add type by location. Once in Revit, you can use the top face to make a roof by the Roof by Face command:
And while the mass will update with Grasshopper, the Roof will need to be updated by re-building the Roof on face by editing it.