Warm the olive oil in a large, heavy saucepan over medium heat. Add the onion, carrot, and celery and season well with salt and pepper. Sauté until the vegetables are soft, 6-8 minutes.

Add the garlic and thyme springs and sauté just until the garlic is soft, about 2 minutes. Pour in the broth, raise the heat to medium-high, and bring to a boil. Add the tortellini and cook until the pasta is al dente, about 7 minutes or according to package directions. Discard the thyme sprigs.

Ladle the tortellini in broth into shallow bowls and garnish with the pecorino; serve hot.