fondant and rolled butter cream are two very different things. i havent used rolled buttercream, and i cant remember what i actually read about it, but theres plenty of posts on here about it. as always, it comes down to what you like eating, and what you like working with - and i dont think rolled buttercream stacks like fondant cookies will do.
if the cookies are still warm, the fondant will stick to it. other wise a bit of water or piping gel will do the job. (can ue icing if you want, but then you are really giving your self more work!)
i think the rolled bc will stick its self.