Bring a large pot of salted water to a boil, then cook the pasta shells for 8-10 minutes until just al dente. Drain and set aside to cool slightly.
While the pasta cooks, chop the roasted red peppers, sautéed spinach, and finely dice the zucchini. Mince the garlic and set all the vegetables aside.
In a mixing bowl, combine ricotta cheese, half a cup of shredded mozzarella, the chopped vegetables, dried Italian herbs, salt, and pepper. Mix until well blended and the filling is creamy.
Using a spoon or piping bag, carefully stuff each shell with the vegetable and cheese mixture, pressing gently to fill completely. Place the filled shells upright in your baking dish, snug but not crowded.
Pour the tomato sauce evenly over the stuffed shells, covering them completely. Sprinkle the remaining mozzarella on top for melty cheesiness.
Cover the dish with aluminum foil and bake at 180°C (350°F) for 25-30 minutes until bubbling and the cheese is golden and melted.
Remove from the oven, uncover, and let rest for 5 minutes. This helps the filling set and makes serving easier.
Garnish with fresh basil or herbs if desired, then serve warm with a side salad or crusty bread. Enjoy the colorful, veggie-packed goodness!