1. Heat broiler. Cover broiling pan with aluminum foil. In large bowl, combine eggplant slices, olive oil, and salt. Place eggplant slices on broiling pan, and broil until tender, about 7 minutes. Let rest 10 minutes, or until cool enough to handle.
2. Heat oven to 375 degrees F. Squeeze any excess liquid from spinach, and place in medium bowl. Add cheeses, garlic, and pepper. Stir to combine.
3. Place 2 tablespoons of spinach mixture onto center of each eggplant slice. Carefully roll up eggplant slices, and place end-side down in casserole pan. Brush with marinara sauce, and bake until cheese melts, about 12 minutes.