Preheat the oven to 400°F. On a rimmed baking sheet, toss together the cauliflower, 2 tablespoons olive oil, and ½ teaspoon salt. Roast for 20 to 25 minutes, turning the cauliflower midway through, until golden brown and cooked thoroughly. Set aside.
Bring a large pot of salted water to a boil. Add the pasta and cook for 10 to 12 minutes, or until al dente. Drain well, reserving 1½ cups of pasta water.
Heat a large sauté pan over medium heat. Add the bread crumbs and toast until fragrant and golden brown, about 3 minutes. Remove to a small bowl and mix with 2 tablespoons Parmesan cheese.
In that same large sauté pan, heat the remaining 3 tablespoons olive oil over medium-high heat. Add the garlic and anchovies and stir with a wooden spoon, breaking up the anchovies to help them dissolve in the oil. This will take about 2 minutes. Add the chili flakes and the cauliflower and toss gently to coat.
Add to the pan the cooked pasta, half of the reserved pasta water, remaining ½ cup cheese, and the parsley. Toss to coat, and simmer for another 2 minutes, adding additional pasta water as needed to moisten. Sprinkle with the bread crumb mixture and drizzle with more olive oil if desired.