Preheat oven to 400 degrees F (200 degrees C). Lightly grease a baking sheet.
Separate crescent rolls into individual triangles.
In a small bowl, mix together cinnamon and sugar.
Dip a marshmallow into melted butter, then roll in sugar mixture. Place marshmallow into the center of a dough triangle. Carefully wrap the dough around the marshmallow. Pinch the seams together tightly to seal in marshmallow as it melts. Place on a baking sheet. Repeat.
Bake in a preheated oven until golden brown, about 15 minutes.