Brown the sausage and drain if needed. Mix with 1 1/2 jars of spaghetti sauce.
Pour half of unmixed sauce into bottom of 9 x 13 baking dish, covering bottom completely. Add a layer of noodles (uncooked), then spoon dollops of ricotta on top of noodles. Cover with 1/2 sausage/sauce mixture, being sure to cover noodles thoroughly. Add another layer of noodles, ricotta, sausage/sauce mix. Add a last layer of noddles and cover with remaining unmixed sauce. Sprinkle mozarella cheese over top liberally.
Cover with tin foil and bake at 350 for 45 minutes, removing tin foil for last 15 minutes to brown cheese. Can be assembled ahead of time.