Preheat your oven to 350°F and line a baking sheet with parchment paper.
Unroll each cinnamon roll and cut it in half. Roll each half back up into a smaller cinnamon roll and place them on the prepared baking sheet. Pillsbury Grands bake up quite large, so cutting them in half makes them a more manageable size. If you are using smaller cinnamon rolls, you can skip this step.
Bake for 8–12 minutes, or until the cinnamon rolls are puffed and lightly golden around the edges.
While the cinnamon rolls are baking, break each pretzel in half to create two C-shaped pieces for the reindeer's antlers.
Drizzle the icing over the warm cinnamon rolls.
While the icing is still soft, quickly press two candy eyes and one red M&M onto each cinnamon roll to make the reindeer's face. Add two pretzel pieces at the top for the antlers.
Let the icing set for a minute, then serve and enjoy!