Preheat the oven to 350°F and coat a 9x13 baking dish with cooking spray.
Cook the lasagna noodles in salted boiling water according to package instructions. Drain and lay them separately on parchment paper.
While the noodles cook, heat olive oil in a large skillet over medium-high heat.
Add the mushrooms and onions, cooking for about 7-8 minutes, stirring occasionally, until the onions soften and the mushrooms turn golden.
Stir in the minced garlic and spinach, cooking for 1-2 minutes until the spinach is wilted.
Remove from heat, season with sea salt and freshly cracked pepper, and set aside to cool.
In a bowl, mix the ricotta cheese, basil, mozzarella, parmesan, egg, nutmeg, sea salt, and freshly cracked pepper until well combined.
To assemble the lasagna roll-ups, spread a portion of the ricotta mixture evenly over each noodle.
Layer the sautéed veggies on top of the ricotta mixture.
Spoon some marinara sauce into the bottom of the prepared baking dish.
Carefully roll up each noodle and place it seam-side down in the dish.
Top each roll-up with marinara sauce and a sprinkle of mozzarella cheese.
Cover the dish with foil and bake for 15 minutes.
Remove the foil and bake for another 5-10 minutes.
Take the dish out of the oven, garnish with fresh parsley, and serve. Enjoy!