Preheat your oven to 425°F (220°C).
Rinse the cauliflower florets under cold water and pat them dry.
In a large bowl, whisk together olive oil, melted butter, minced garlic, salt, black pepper, smoked paprika, and optional red pepper flakes.
Add the cauliflower florets into the bowl and toss well until coated.
Arrange the coated florets on a baking sheet in a single layer and roast for about 20–25 minutes, flipping halfway through.
Once fork-tender and golden, drizzle lemon juice over the cauliflower.
Serve hot alongside your favorite main dish or enjoy as a standalone side.