1. Heat oven to 400 degrees F.
Cauliflower:2. In large bowl, toss together the cauliflower flowerets, olive oil, salt and pepper until cauliflower is well coated. Transfer to large rimmed baking sheet, at least 15 x 10 x 1 inches.
3. Roast cauliflower in 400 degree F oven, stirring occasionally, for 30 minutes or until the cauliflower is tender and evenly browned.
Sauce:4. Near end of the roasting time, in medium-size saucepan, melt butter over medium heat. Sprinkle the flour over the butter in the saucepan; whisk until the flour and butter are blended and the mixture is slightly brown, about 3 minutes. Gradually whisk in the milk until smooth. Add salt, pepper and nutmeg; simmer, whisking occasionally, 3 minutes. Remove the saucepan from the heat. Whisk in the cheese and cayenne until the cheese is melted and well blended.
5. Transfer the cauliflower to a large serving platter. Spoon the sauce over the cauliflower. Sprinkle the parsley over the top as a garnish, if desired. Serve immediately. Makes 8 servings.