Preheat the oven to 375°F (190°C). Line a baking sheet with foil.
Place the meatballs on the prepared baking sheet. Bake for 30 minutes, or until the internal temperature reaches 165°F (75°C).
Bring 4 quarts of salted water to a boil in a large pot. Add the tagliatelle and return the water to a boil. Cook uncovered, stirring occasionally, until the pasta is tender, about 9 minutes. Remove from the heat and strain.
In a medium saucepan over medium heat, bring the marinara sauce to a simmer.
Serve the pasta with the meatballs, sauce, and mozzarella.