Preheat oven to 425 degrees Fahrenheit. Line a large rimmed baking pan with parchment paper. Spread cauliflower florets in an even layer. Drizzle with olive oil, season with salt and pepper, and toss to coat. Bake for 30 minutes. Cauliflower should have charred, crispy bits on tips.

Lower heat to 400 degrees Fahrenheit. Spray a 9x13 baking pan or 2-quart casserole dish with cooking spray. Spread a ½ cup of the pasta sauce over the bottom. Layer a ½ cup of the Parmesan cheese on top. Add half of the roasted cauliflower in an even layer, followed by ⅓ cup of the mozzarella cheese. Top with 1 ½ cups of pasta sauce, followed by ½ cup (minus a couple tablespoons for topping) of remaining Parmesan cheese. Add remaining cauliflower, then mozzarella cheese, followed by remaining ½ cup of pasta sauce. Sprinkle with reserved tablespoons of Parmesan.

Bake for 20 to 25 minutes, or until sauce is bubbling and cheese is melted.