Preheat oven to 375 degrees F. Spray two baking sheets with nonstick spray or line with parchment paper. Set aside.
Place eggplant slices on prepared baking sheets in single layer. Brush both sides of eggplant slices with olive oil. Bake until eggplant slices are tender and beginning to brown (about 5 minutes per side). Watch closely and remove eggplant slices as needed if they are cooking too quickly or not long enough. Remove baking sheets from oven and cool eggplant while preparing sauce. Eggplant can be roasted 1 day ahead and refrigerated.
In a large sauce pan, brown ground beef over medium heat. Drain excess grease.
Return pan to heat and add onion, garlic and mushrooms. Stirring frequently, brown and cook until onions and mushrooms are tender (about 5 to 10 minutes).
Add diced tomatoes along with juice, tomato paste, oregano, basil, salt, pepper, parsley and spinach. Bring to a simmer.
Allow to simmer for about 10 minutes, stirring frequently. Sauce can be made several days ahead and refrigerated.
Spread 2 cups of the meat sauce in the bottom of a 9"x13" baking pan. Layer 4 slices of eggplant on top of the sauce.
Spread another 2 cups of sauce on top of the eggplant slices. Arrange a second layer of eggplant slices directly on top of the first layer, stacking them.
Spoon remaining sauce on top. Cover with foil and refrigerate until ready to cook. This can be constructed up to one day in advance.
Bake eggplant lasagna until heated through, about 25 to 30 minutes if freshly made or 40 minutes if refrigerated. Serve hot topped with fresh parsley.