Preheat the oven to 425 degrees . On a rimmed baking sheet, toss the cauliflower with 1/4 cup olive oil and season with salt and pepper. Roast, stirring halfway through, until browned, 20 to 25 minutes. Remove from the oven. Lower the temperature to 350 degrees .
Meanwhile, in a large pot of boiling, salted water, cook the ziti until al dente. Drain, reserving 1/2 cup of the cooking water. Return the pasta and cooking water to the pot and stir in the crushed tomatoes, feta, olives, the remaining 1/4 cup olive oil and half each of the parsley and bread crumbs.
Pour the mixture into a 2-quart baking dish; top with the roasted cauliflower and remaining bread crumbs. Bake until heated through, about 10 minutes. Sprinkle the remaining parsley on top.