Preheat the oven to 350°F.

Combine spinach, ricotta, Parmesan cheese, egg, garlic, Italian seasonings, chicken (if using), and salt and pepper in a medium bowl. Pour about 1 cup of the spaghetti sauce on the bottom of a 9×13 glass baking dish.

Place a piece of wax paper on the counter and lay out the lasagna noodles. Make sure they are dry by patting them with a paper towel. Take 1/3 cup of the ricotta mixture and spread evenly over a noodle.

Roll carefully and place seam side down onto the baking dish. Repeat with remaining noodles.

Ladle sauce over the noodles in the baking dish and top each one with 1 Tbsp. of mozzarella cheese. Cover the baking dish tightly with aluminum foil and bake for 40 minutes, or until the cheese melts. Serve hot.