Roasted Cauliflower Pasta with Anchovy Garlic Sauce

For the Roasted Cauliflower:

• 6 cups (about) cauliflower florets, from 1 medium cauliflower
• 1/4 cup extra-virgin olive oil
• 1 teaspoon salt
• 1/2 teaspoon black pepper

For the Pasta:

• 8 ounces dried spaghetti, cooked al dente
• Salt, for the water

For the Anchovy Garlic Sauce:

• 1/4 cup olive oil
• 6 cloves garlic, minced
• 1 (2-oz.) tin oil-packed anchovies
• 1/2 teaspoon (or more if you like it hot) crushed red chile flakes
• 1 roasted red pepper, diced
• 2 tablespoons capers, rinsed
• 2 tbsp. butter, cubed
• 3 tbsp parsley, finely chopped
• Salt and freshly ground black pepper, to taste
• Freshly shaved parmesan, for garnish
• 1/4 cup reserved pasta water