Preheat your oven to 425°F (220°C) and bring a large pot of salted water to a boil.
In a large mixing bowl, combine zucchini, eggplant, and red onion. Drizzle with 2 tablespoons of olive oil, season with salt and pepper, and toss to coat. Spread on a baking sheet.
Roast the vegetables for 15 minutes, then add the tomatoes, toss with remaining olive oil, and roast for another 15 minutes.
While the vegetables roast, cook the mezze rigatoni according to package instructions until al dente. Reserve 1 cup of pasta water before draining.