I have to make some very thin fondant rope/yarn today for a cake. I didn't think it through how I would go about making it that thin-so now I am in a pinch. Should I just roll it out and make it super thin, or is there another utensil I could use?

I have used a pasta machine to get the fondant thin for small things like the rope or fondant decorations that are small. just make sure you pat it think or roll it out like you would the pasta dough so it don't get stuck.

If you happen to have a clay extruder… ($9-$10 at any craft store for a basic one) that would work.  Otherwise I might add in some shortening to make the fondant less dry and very pliable and just roll it by hand THIN, and maybe sort of braid or twist two thin pieces together so it looks woven.