In large bowl, mix 2 tablespoons of the melted butter, 1/4 teaspoon of the salt and 1/4 teaspoon of the pepper. Add potatoes and cauliflower; toss to coat. Place cauliflower and potatoes (skin sides down) in single layer in pan. Roast 16 to 18 minutes or until just tender when pierced with knife. Remove from oven; stir.