After watching several videos, if someone else needs to calculate the roof surface area, the following is what I found to be the easiest method:
1.) Select all the roofs.
2.) In Archicad, go to: Window -> Palettes -> Element Information
3.) When "Element Information" comes up, make sure the only option selected is: Element's Surface.
4.) Look at the area amount for each Roof Surface under the line that says: "Surface, Top, Conditional".
Adding up all the areas under "Surface, Top, Conditional" will give the roof area for roofing material such as Shingles, Roof Sheathing, etc.
Hope This Helps.