Preheat oven to 400°.
Cut the top and bottom off the butternut squash and peel remaining skin. Slice lengthwise into large 1/4-inch strips, cutting out the stringy center.
Lay squash slices in a single layer on foil-covered baking sheets. Lightly brush the tops with olive oil and sprinkle with salt.
Roast squash at 400° for 15 minutes, until centers are soft and edges are beginning to brown. Flip slices over, brush with oil and salt, and roast another 15 minutes.
While squash is roasting, brown the sausage in a large pan. Drain any excess grease until there is about a tablespoon remaining, then add spinach, onion, garlic, and spices. Cook over medium heat until the spinach is wilted and the onion is cooked.
Transfer the sausage mixture to a large bowl. Cream together with ricotta and 1 cup mozzarella.
Layer sausage mixture and eggplant slices in a greased 9x13 pan, starting with sausage and ending with eggplant. Sprinkle remaining 1 cup mozzarella on top.
Bake at 400° for 15-18 minutes, until edges are bubbling and cheese is beginning to brown.