Does Ganache go under fondant, or can it be a coating for cakes, then the roses, and decorations are added? I think it'd be kind of cool to coat a cake, like cake pops are coated, then make flowers, or lace or whatever over the top.

Actually there are two kinds of ganache - the kind you use under fondant, which is thick and spreadable, and the pourable kind, which is thin and can be either poured or spread thinly over a cake. They both make admirable icings in their own right. Go for it!