Step 1: Prepare the Noodles and Oven

1. Preheat Oven: Preheat your oven to 375°F (190°C).
2. Cook the Lasagna Noodles: Bring a large pot of heavily salted water to a rolling boil. Add the lasagna noodles and cook according to the package directions, but aim for al dente (firm to the bite). It’s crucial not to overcook them, as mushy noodles will tear easily during rolling. Cook a few extra noodles just in case.
3. Drain and Rinse: Once cooked, carefully drain the noodles. Immediately rinse them with cold water to stop the cooking process and wash away excess starch. This is a key step to prevent them from sticking together.
4. Prevent Sticking: Lay the cooked noodles in a single layer on baking sheets or parchment paper. Drizzle them with a little olive oil and gently toss to coat. This will ensure they stay separated and pliable while you prepare the filling.

Step 2: Make the Creamy Spinach Ricotta Filling

1. Dry the Spinach: Place the thawed spinach in the center of a clean kitchen towel, cheesecloth, or several layers of heavy-duty paper towels. Gather the ends and twist tightly, squeezing out as much liquid as humanly possible. You will be surprised by how much water comes out. This is the single most important step for achieving a thick, creamy filling, not a watery mess.
2. Combine Filling Ingredients: In a large bowl, combine the whole milk ricotta, the squeezed-dry spinach, 1 cup of the shredded mozzarella, ¼ cup of the grated Parmesan, the minced garlic, the large egg, Italian seasoning, salt, pepper, and the ground nutmeg.
3. Mix Thoroughly: Stir everything together until it is well combined and evenly distributed. Taste the mixture and adjust the salt and pepper if needed.

Step 3: Assemble the Lasagna Roll-Ups

1. Prepare the Baking Dish: Spread about 1 cup of your marinara sauce evenly over the bottom of a 9×13 inch baking dish. This sauce layer prevents the roll-ups from sticking and ensures they stay moist while baking.
2. Fill the Noodles: Lay one cooked lasagna noodle flat on your work surface. Spread about ¼ cup of the spinach-ricotta mixture evenly over the entire surface of the noodle, leaving a small ½-inch border at one end.
3. Roll it Up: Starting from the end with the filling, gently but snugly roll up the noodle into a spiral. Don’t roll it too tightly, or the filling will squeeze out.
4. Place in the Dish: Place the rolled-up noodle seam-side down into the prepared baking dish. Repeat the process with the remaining noodles and filling, arranging them snugly in the dish. You should be able to fit about 12-14 roll-ups.

Step 4: Bake to Bubbly Perfection

1. Top with Sauce and Cheese: Spoon the remaining marinara sauce over the top of the roll-ups. You can cover them completely or leave some of the pasta edges exposed for a nice texture contrast.
2. Add Cheese: Sprinkle the remaining ½ cup of mozzarella cheese and ¼ cup of Parmesan cheese evenly over the top.
3. Bake: Cover the baking dish tightly with aluminum foil. This traps the steam and helps the roll-ups cook through without drying out. Bake for 25-30 minutes.
4. Brown the Top: After 30 minutes, carefully remove the foil. Return the dish to the oven and bake for another 10-15 minutes, or until the cheese is melted, bubbly, and starting to turn golden brown on top.
5. Rest Before Serving: This is a crucial final step! Let the lasagna roll-ups rest in the pan for at least 10 minutes before serving. This allows them to set, making them easier to serve cleanly and preventing them from falling apart.
6. Garnish and Serve: Garnish with fresh chopped basil or parsley for a pop of color and fresh flavor before bringing it to the table.