Combine sugar and cinnamon in a small bowl.
Unroll crescent roll dough, and separate each roll along perforations.
Roll marshmallows in melted butter, and then in cinnamon-sugar mixture. Place one coated marshmallow in the middle of an unrolled crescent dough segment, and roll the marshmallow until completely covered by the dough, pushing in sides as you go. Pinch seams on either end to seal each roll.
Place rolls on a jellyroll pan, and bake at 350˚ for about 12 minutes.
Immediately after removing rolls from the oven, brush with remaining melted butter and then sprinkle with remaining cinnamon-sugar mixture. Serve warm.