Preheat the oven to 400 degrees F (200 degrees C). Lightly grease a baking sheet.

Separate crescent rolls into individual triangles.

Mix sugar and cinnamon together in a small bowl.

Dip a marshmallow into melted butter, then roll in sugar mixture. Place marshmallow into the center of a dough triangle; carefully wrap dough around marshmallow. Pinch the seams together tightly to seal in marshmallow as it melts. Place roll on a baking sheet; repeat with remaining dough and marshmallows.

Bake rolls in the preheated oven until golden brown, about 15 minutes.