Line a baking sheet with a double layer of paper towels and sprinkle with 1 tablespoon of the coarse salt. Lay the eggplant slices in a single layer on the towels. Sprinkle the top of the eggplant with the remaining coarse salt. Let the eggplant stand for 30 minutes, discard the paper towels and brush off the salt. Brush the eggplant with 2 tablespoons of the olive oil, place back on the baking sheet and roast for 15-20 minutes until moist and beginning to brown. Remove from oven, cool and cut into cubes.
Meanwhile, cook the pasta in a large pot of well salted boiling water until al dente. In a large skillet, sauté the sausage over medium-high heat in the remaining tablespoon of oil for 4-5 minutes. Add the spinach and cook until wilted (about 30 seconds). In a large mixing bowl combine the sausage, spinach, tomatoes, eggplant and ricotta. Mix the pasta with other ingredients in the bowl. Season to taste with salt and pepper. Place in a shallow baking dish, sprinkle the top with Parmesan and bake for 20 minutes until bubbling.