Toss the eggplant, zucchini, summer squash, tomatoes and cauliflower with 3 tablespoons olive oil, 1 tablespoon salt and 1/2 teaspoon pepper on a sheet pan lined with parchment paper. Roast for 40 minutes, or until the vegetables are soft and slightly browned, stirring once halfway through.
Heat 2 tablespoons in a large cooking pot over medium heat. Add the onion, 1 teaspoon salt and 1/2 teaspoon pepper. Saute onions for approximately 5 minutes until soft. Add the peppers and saute for approximately 7 minutes until soft. Reduce heat to low.
Add roasted vegetables to the pot and add vinegar, lemon juice, basil and thyme. Add any additional salt, pepper, or olive, according to taste. Let stew flavors come together over low heat for about 10 minutes, stirring occasionally.
Meanwhile bring 4 1/2 cups water to a boil in a medium pot, adding salt. Slowly whisk the polenta in and reduce heat to low. Stir polenta frequently for about 12 to 15 minutes until cornmeal is thick and soft, then remove from heat. Add the cheese, milk and butter and stir very well until cheese and butter have melted. Stir in thyme, basil and crushed red pepper and mix very well.
Serve the roasted vegetable stew over the herbed polenta in wide bowls. Sprinkle freshly grated parmesan cheese on top.