Preheat oven to 425 degrees, with racks in upper and lower thirds. On a rimmed baking sheet, toss together 2 tablespoons oil, cauliflower, and chickpeas; season with salt and pepper. Arrange cauliflower and chickpeas in a single layer and roast until cauliflower is tender and chickpeas are crunchy, 25 minutes. On another rimmed baking sheet, arrange bread in a single layer and toast until golden and crisp, 10 minutes.
Meanwhile, in a large pot of boiling salted water, cook pasta until al dente. Drain pasta and return to pot. Add cauliflower mixture, 2 tablespoons oil, and parsley. Season with salt and pepper and toss to combine. To serve, top with croutons and ricotta, then drizzle with oil.