Preheat oven to 400°. Spread cauliflower florets on a sheet pan leaving some space between them. Drizzle with olive oil and sprinkle with salt and pepper. Roast for 30 minutes, or until fork tender.
Grease a small baking dish. (I use a 7½" souffle dish.)
In a small saucepan, heat the cream until it's just beginning to boil. Remove from the heat and add the cheese a little at a time, stirring until the cheese melts. Add salt and pepper to taste.
When the cauliflower is done, transfer to the prepared baking dish and lower the oven to 350°. Pour the cheese sauce over the cauliflower. Toss the crumbs with the melted butter and sprinkle evenly over the casserole. Dust the top with paprika if using. Bake 25-30 minutes until the sauce is bubbly and the crumbs are browned.