Place florets on a baking sheet; drizzle with olive oil, salt, and pepper. Toss well to coat. Roast for 35-45 minutes or until tender and beginning to brown.
Meanwhile, combine cashews, water, garlic, marinara, roasted red peppers, and crushed red pepper in a blender and process until smooth.
Bring a large pot of water to a rolling boil. Cook pasta until al dente, according to package directions. Drain and keep hot.
Pour sauce over pasta and cauliflower; gently toss to coat.