Bring a large pot of salted water to a boil. Add the frozen tortellini and cook according to package instructions, usually about 3-5 minutes. Drain and set aside.

In a skillet, heat olive oil over medium heat. Add minced garlic and sauté for 1 minute until fragrant.

Add the diced tomatoes (with juice), spinach, oregano, salt, and pepper. Simmer for 5-7 minutes until the spinach is wilted and the sauce is heated through.

Add the cooked tortellini to the skillet with the sauce. Toss gently to combine and heat through for 2-3 minutes.

Serve hot, topped with grated Parmesan cheese.