My friend is trying to make a sheeter, but he's never seen one in real life, only on the net.  Can anyone who has one tell me, if you turn the handle do both rollers turn with no fondant between them? Or does the top one only turn when there is fondant there?

Think giant pasta roller.

Both rollers have to move to pass the fondant through.

But I think the question is will the second roller roll with the pressure of the material and the second rollercausing the movement. I believe if it moves freely without binding that it would. But it would be simple enough to put a gear/cog on the side to make them roll simultaneously independent of the pressure of the fondant.

I'm pretty sure mine both roll when the machine turns on, both motorized. Mine is the big sommerset. 

Thanks for your help guys!  Wish we could see one up close, but don't know anyone with one.

There's a video with this slab roller [some use them as "sheeters" for fondant] that might help:

http://www.baileypottery.com/slabrollers/drd2.htm#Mini