Prepare the marinara sauce (below) and cook the lasagna noodles according to the package directions. Preheat oven to 350°F.
Using a large saucepan, sauté the onion in olive oil on medium-low heat for about 3-5 minutes or until the onion turns translucent.
Then add the garlic and continue cooking for another minute, stirring often.
Add the mushrooms, sage, salt, and pepper. Cook for 5-6 minutes until the mushrooms are tender and beginning to give up their juices.
Then add the spinach to the skillet and continue to cook until it wilts (about another 5 minutes).
Transfer the contents of the skillet to a large bowl and mix in the cottage cheese, and Parmesan. Adjust salt and pepper as needed.
Scoop about one cup of marinara sauce in the bottom of a 9×13 pan and spread it around. Lay the lasagna noodles on a large cutting board or piece of freezer paper. Scoop about 1/3 cup of the filling onto each noodle and spread out. Roll each noodle and place in the pan, seam side down.
Scoop another cup and a half of marinara sauce over the rolls and top the pan with shredded mozzarella.
Cover the pan with aluminum foil or an oven safe lid and bake for 40 minutes or until the cheese is melted. Remove foil and continue baking until the cheese is browned. Let cool for a few minutes before serving.