Preheat oven to 400° F. Bring a large pot of water to a boil. Place the zucchini in a large baking dish in a single layer and drizzle with the oil, chili flakes, and 3 tablespoons of the Parmesan, then season with the pepper and ½ teaspoon of the salt. Add the garlic and roast for 20 minutes, tossing halfway through, until tender and just golden brown. Meanwhile, add the ravioli and the remaining salt to the boiling water. Return to a boil, stirring frequently to prevent the ravioli from sticking. Cook the ravioli for 3 minutes after they begin to float. Drain and place in a large bowl. Toss gently with the roasted zucchini, half the parsley, and half the remaining Parmesan. Serve immediately with the remaining parsley and Parmesan.