Prepare oven and baking sheet: Preheat oven to 350°F, and line a baking sheet with parchment paper.
Make cinnamon-sugar mixture: Combine sugar and cinnamon in a small bowl.
Prepare crescent rolls: Unroll crescent roll dough, and separate each roll along perforations.
Coat marshmallows in cinnamon-sugar mixture: Roll marshmallows in melted butter, and then in cinnamon-sugar mixture.
Roll marshmallows in dough: 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 each rolls, evenly spaced, on prepared baking sheet.
Bake rolls: Bake at 350°F for about 12 minutes.
Brush with butter, and sprinkle cinnamon-sugar mixture: Immediately after removing rolls from the oven, brush with remaining melted butter, and then sprinkle with remaining cinnamon-sugar mixture. Serve warm.
