3D (rendering?) question

you'll have to model it if you want thickness to the tiles because autocad doesn't do displacement/bump mapping. But if your not bothered about that then you could always map a pic of roof tiles onto the roof no problem (I will look pretty crap though if your rendering in autocad no matter what you do).

I agree....besides, the ARRAY command is pretty fast. I'd model it if it was very important to me.

What about "bump map" in material options?

Never figured out how to use that.

bump mapping adds bumps to maps only, NOT your geometry, so in this case you can make the map of the tiles have more shadows and generally look more 3Dish, but it will not change the geometry, like displacement mapping in other programs such as 3ds max would, so the ridge and gutter lines of your roof will still look flat.