cheezz, don't roll it too thin. Dust heavily with blend of cornstarch and powdered sugar
to keep it from sticking. For the 6" circumference, you'll need about 19". You can roll it out, cut the width and then the length and then gently fold it up like transferring a pie crust to its pan. Maybe three folds? BE sure to have a brush and water ready to dampen the fondant-covered cake to get the ribbon to stick. The biggest thing is not to let it drape on its own because the weight will pull it out of shape.
A second method--and one I would use-- would be to simply use two lengths of 9.5" each. Where they meet in front will be covered with the bow; where the two pieces meet in back can be decorated with pearls of icing. This length will be easier to manage on the larger diameter.
Good luck.