Use a clay extruder or roll long ropes of fondant out. Let it sit a couple of minutes so it is not real sticky and then lay the ropes side by side and put your hands on both ends of the rope. Push one hand forward and the other backwards on the rope ends and it will twist it up pretty as you please.
I forget where I read or saw this tip, but to make perfect rolls of fondant by hand, shape fondant into a cigar shape, then roll over it with your fondant smoother. If the cigar won't roll, ever so lightly grease the work surface with just a smidgeon of Crisco. It also helps to pull very gently on one end of the rope with one hand while you roll the smoother back and forth over the rope with the other.
You can also get a mold for it--much easier and more consistent.
What a pretty cake!
I bought the mold for this rope boarder from First Impressions, and I LOVE it! It has two rope boarders in a 1 piece mold. Really easy to use too, and always comes out perfect!!!!