1. Preheat oven to 350 degrees F. Spray a 9 by 13 baking dish with cooking spray and set aside.
2. To make the filling-in a large sauce pan heat olive oil over medium-high heat. Add onion and garlic, cook until tender, about five minutes. Stir in spinach and mushrooms, cook until mushrooms are soft and spinach is wilted, about five minutes. Remove from heat.
3. In a large bowl, stir together ricotta cheese, mozzarella cheese, and parmesan cheese. Add egg and mix until well combined. Stir in spinach mushroom mixture and seasonings. Set aside while you make the sauce.
4. To make the sauce-in a large stockpot heat olive oil over medium-high heat. Add onion and garlic and cook for about five minutes. Add red pepper flakes, fennel seeds, and diced tomatoes. Stir in tomato paste. Add fresh basil and season with salt and pepper. Simmer on stove for about 20 minutes.
5. For the pasta-add lasagna noodles to a large pot of boiling water that has been salted. Cook for three minutes or until the noodles are al dente. Do not overcook, they will finish cooking in the oven. Carefully remove noodles from water and lay flat on a wire cooling rack.
6. To assemble the cannelloni-spread about a 1/2 cup of the sauce in the baking dish. Spread about 1/4 cup spinach ricotta filling in a line along one short side of the lasagna noodle. Put 1 tablespoon of sauce on top and then roll up to enclose filling. Carefully transfer cannelloni to pan and place seam side down. Continue stuffing and rolling remaining cannelloni. Top cannelloni with remaining sauce and 1 1/2 cups mozzarella cheese. Cover pan with foil and bake until sauce is bubbling, about 30 minutes. Remove foil and bake for 5 additional minutes, until cheese is melted.
Note-Cannelloni can be assembled (but not baked) one day ahead. Chill and keep in the refrigerator. Let stand at room temperature 15 minutes before baking. It also freezes well.