Preheat the oven: Preheat your oven to 425°F (220°C).
Slice the zucchini: Remove the stems and carefully slice the zucchini lengthwise into approximately 1/8-inch-thick strips. A mandoline makes it easier to achieve even slices, but a sharp knife can also be used.
Remove excess moisture: Arrange the zucchini slices in a single layer on a baking sheet. Lightly sprinkle with salt and let them sit for about 5 minutes. Bake for 1 minute to soften the slices and encourage excess moisture to release. If your slices are thicker, they may need a few additional minutes.
Pat the zucchini dry: Remove the zucchini from the oven and thoroughly pat the slices dry with paper towels.
Make the filling: In a bowl, combine the ricotta, 1/2 cup Parmigiano Reggiano, basil, parsley, garlic, egg, salt, and black pepper. Stir until well combined.
Prepare the baking dish: Spread about 1/2 cup of marinara sauce over the bottom of a large baking or casserole dish.
Fill and roll: Overlap two zucchini slices to create a wider surface. Spread approximately 1 tablespoon of the cheese filling over the zucchini, then gently roll it up. Place each roll seam-side down in the prepared baking dish.
Add the toppings: Spoon 1–2 tablespoons of marinara over each rollatini. Sprinkle the mozzarella and remaining 1/2 cup Parmigiano Reggiano evenly over the top.
Bake: Bake uncovered for 25–30 minutes, or until the zucchini is tender and the cheese is melted, bubbling, and lightly browned.
Serve: Let the rollatini rest for a few minutes, then garnish with fresh basil and serve warm. These Three Cheese Zucchini Rollatini are especially delicious with a simple green salad or crusty bread.