Preheat oven to 425°. Place the eggplant cubes in one baking dish (large enough that everything is in one layer). Drizzle generously with olive oil and immediately toss well to coat before all the oil absorbs in one place. Season with salt, pepper and crushed red pepper if using.
Cut out and discard any damaged or rotten parts of your tomatoes. Place the tomato chunks, onion, bell pepper quarters and garlic cloves in a separate baking dish. Drizzle with the olive oil and shimmy the dish around to coat everything well. Season generously with salt and pepper. Roast both dishes for approximately 30 minutes. Stir eggplant once. Continue roasting for up to another 30 minutes until tomatoes are broken down and starting to caramelize and until eggplant is caramelized. Remove from oven. (Eggplant may come out before tomatoes are fully caramelized).
Let everything cool down a bit. Carefully transfer contents of both dishes to a blender or food processor (should not be steaming anymore). Blend to desired consistency. I like to add a little more olive oil during processing for richness. Add basil, sugar and cinnamon, process again. Adjust seasoning to taste.
Place a gallon zip loc bag into a medium bowl or a medium Pyrex measuring cup. Fold the opening over the edges of your vessel. Pour the sauce into the ziploc. Remove ziploc from bowl and carefully roll up lengthwise as you seal to ensure as much air is out as possible. Freeze. Thaw in refrigerator before heating up to use on spaghetti. Should make about 2-3 cups of sauce.
Notes
Use up those damaged or staring-to-go garden tomatoes in this rich spaghetti sauce that can be frozen now and thawed out on cold winter nights.