1-Preheat the oven: Preheat the oven to 350 degrees F.

2-Cook the noodles: Cook the 12 lasagna noodles in boiling salted water until al dente, then drain and lay them flat to cool.

3-Prepare the béchamel sauce: melt 5 tablespoons unsalted butter over medium heat, whisk in 1/3 cup all-purpose flour, and cook for one minute. Gradually add 4 cups whole milk while whisking, bring to a boil, then simmer until thickened (about 8-10 minutes). Season with a pinch of ground nutmeg and kosher salt to taste, then set aside.

4-Mix the ricotta filling: In a bowl, mix 2 cups ricotta cheese, 1 large egg, 1 clove minced garlic, 10 ounces thawed and drained frozen spinach, 1/2 cup pesto, 1/4 cup parmesan cheese, 1/8 teaspoon crushed red pepper flakes, a pinch of nutmeg, and salt and freshly ground black pepper to taste until well combined.

5-Prepare the baking dish: Spray a 9×13 inch baking dish with cooking spray and spread 1/2 cup of the béchamel sauce at the bottom.

6-Assemble the roll ups: On each lasagna noodle, spread about 1/4 cup of the ricotta-spinach mixture evenly, top with 2 tablespoons shredded mozzarella cheese and 2 tablespoons béchamel sauce, then roll up and place in the dish.

7-Top the rolls: Cover the rolls with the remaining béchamel sauce, the remaining shredded mozzarella cheese, and the remaining 3 tablespoons parmesan cheese.

8-Bake the roll ups: Spray foil with cooking spray, cover the dish, and bake for 30 minutes. Remove the foil and bake for an additional 5 minutes until the cheese is melted and bubbly.

9-Rest and freeze: Let the dish sit for 5 minutes before serving. The rolls can be frozen after cooling for up to one month.