Set your oven to 400°F (200°C) and line your sheet pan with parchment paper or a silicone baking mat.
Divide your frozen meatballs into four equal groups in separate bowls. Add 1 cup of BBQ sauce to the first, 1 cup of pesto to the second, 1 cup of marinara sauce to the third, and 1 cup of buffalo sauce to the last. Toss each group gently to coat the meatballs evenly.
Place each sauced batch of meatballs in distinct sections on the sheet pan to keep the flavors separate and visually appealing.
Pop the sheet pan in the oven and bake for 25-30 minutes, or until the meatballs reach an internal temperature of 165°F (74°C) and the sauces are bubbly.
Once out of the oven, sprinkle shredded parmesan cheese on the marinara and pesto meatballs if desired. Serve with ranch dressing on the side for dipping.