Step 1
Heat 1 tablespoon olive oil in a saucepan over medium heat. Add garlic and red pepper flakes; cook and stir until golden about 1 minute. Stir in basil and oregano; cook until fragrant about 1 minute. Stir in tomato sauce. Simmer sauce until flavors combine about 20 minutes.
Step 2
Combine spinach and 2 tablespoons water in a large skillet over medium heat. Cover and cook until spinach is wilted 3 to 5 minutes. Drain and cool until easily handled about 5 minutes. Gather spinach into a ball and squeeze out excess water. Chop coarsely.
Step 3
Combine chopped spinach ricotta and ½ cup Parmesan cheese in a bowl.
Step 4
Preheat oven to 400 degrees F (200 degrees C). Line 2 baking sheets with parchment paper.
Step 5
Divide eggplant red bell pepper and orange bell pepper between lined baking sheets. Drizzle with 2 tablespoons olive oil and toss to coat. Season with salt and pepper.
Step 6
Roast in the preheated oven stirring every 10 minutes until tender and browned in spots about 30 minutes. Remove from oven.
Step 7
Bring 6 cups water to a boil; add salt. Pour in polenta in a steady stream whisking constantly. Reduce heat to low. Whisk until polenta thickens about 5 minutes. Cover and cook stirring vigorously every 10 minutes until polenta is the consistency of porridge about 30 minutes.
Step 8
Reduce oven temperature to 350 degrees F (175 degrees C). Grease a 9x13-inch baking dish with cooking spray.
Step 9
Spread half the polenta evenly in the bottom of the baking dish. Layer half of the spinach mixture roasted vegetables and sauce on top. Top with ½ cup mozzarella cheese and ¼ cup Parmesan cheese. Repeat layers with remaining polenta spinach mixture roasted vegetables and sauce. Top with remaining mozzarella cheese and Parmesan cheese.
Step 9
Bake in the preheated oven until cheese melts and sauce is bubbly about 20 minutes. Let cool before cutting so layers hold at least 20 minutes.