Lightly grease a baking dish (I used a 9" x 13" dish).
Spread 1/3 of the roasted butternut squash filling evenly across the bottom of the pan, then sprinkle a bit of the mozzarella cheese over the top.
Place a layer of cooked lasagna noodles on top, without overlapping noodles (I cut some noodles to fit into odd spaces to make sure there was a full, even layer of noodles).
Spread half of the spinach mixture on top of the noodles, then sprinkle a bit of the mozzarella cheese across the top.
Place another layer of cooked lasagna noodles on top of the spinach mixture, again without overlapping the noodles.
Spread 1/3 of the roasted butternut squash filling over top of the noodles, then sprinkle a bit of the mozzarella cheese on top.
Place another layer of cooked lasagna noodles on top of the spinach mixture, again without overlapping the noodles.
Spread the other 1/2 of the spinach filling over top of the noodles, then sprinkle a bit more of the mozzarella cheese on top.
Place a final layer of cooked lasagna noodles on top of the spinach mixture, again without overlapping the noodles.
Spread the remaining roasted butternut squash filling over top of the noodles, then sprinkle the remaining mozzarella cheese and the Parmesan cheese over the top.
Cover the baking dish with aluminum foil and bake in the 375 degree oven for 30 minutes.
Remove the foil from the baking dish and continue baking uncovered for ~10-15 minutes until cheese is melted.
Allow lasagna to sit at room temperature for about 10 minutes before cutting.