Cook the pasta shells according to package instructions. (see note for uncooked option)
While the shells are cooking, mix together the ricotta, 1/2 cup mozzarella, romano, egg, spinach, and spices.
Line a 9x13 pan with half of the tomato sauce and set aside.
Drain the pasta shells and rinse them under cold water to prevent sticking (and make handling easier).
Fill each shell with the filling and place it in the dish. Continue until all the shells have been filled.
Pour the remaining sauce on top and sprinkle with the remaining cheese.
Bake uncovered for 10 - 15 minutes until everything is hot and bubbly.
Remove and serve, garnishing with additional pecorino if desired.
Notes
Note: You can skip pre-cooking the shells if you have more time. If you want to go that route, simply fill the uncooked shells with the cheese mixture and follow steps 7-9.