Preheat oven to 450F.
Line a large large baking sheet with foil and spray with oil. Place the cauliflower and the brussels cut side down on the baking sheet, spread with oil and roast on the bottom third of the oven 25 minutes, tossing half way until slightly browned.
Meanwhile, melt the butter in a large sauce pan over low heat and add shallots. Cook baking sheet, spread with oil and roast on the bottom Already Exists 5 minutes.
shut the oven, reserve approximately 1 beneficiant cup of the roasted vegetables and keep warm on the baking sheet.
transfer the relaxation to the pot and simmer 2 minutes.
switch in two batches to the blender and mix until smooth.
Serve in 4 bowls topped with the roasted vegetables and fresh black pepper, to taste. Serve immediately.