Preheat oven to 450°F. Toss cauliflower florets with olive oil on a large baking sheet and season with salt and pepper. Roast, stirring and shaking pan once or twice, until cauliflower is lightly browned, 15 to 20 minutes.
Bring a large pot of salted water to a boil and add pasta. Cook according to package directions or until soft, but not mushy, 10 to 12 minutes; drain in a colander. Return pasta to pot.
Add olives, marinara sauce and cauliflower to pasta in pot. Sprinkle about 1/4 cup Parmesan over pasta and toss. Serve with remaining Parmesan cheese for topping.