Currently revit roof can't host Rebars, in my country (Dominican Republic) and in the majority of Latin America countries we use concrete reinforced roof.
In flat and shed roof we have the workarround of using Revit floor instead of roof, so we can put rebars; but in gable, pitched, hipped, domers or mixed roofs are not easy to create with floors, nor masses (to convert into floors).
So, would be great if you can roof host rebar in the future.
Regards,