Line a roasting pan with foil and spray lightly with cooking oil. Spread cauliflower and carrots onto foil and drizzle with rice bran oil. Sprinkle with salt and pepper. Roast at 400 degrees for 10-15 minutes until softened (but not too soft).
While veggies are roasting, sauté onion in a medium stockpot in 1 tablespoon of oil for 3-4 minutes. Add 1/4 teaspoon ground ginger and stir to coat.
Add vegetable broth and roasted vegetables to onion mixture. Add cayenne to taste. (I'm heavy handed because I like the spice.) Bring to a boil and reduce heat. Cover and simmer 10 minutes. Remove from heat.
Using immersion blender, cream mixture. (Cauliflower is stubborn to cream, so keep at it.) Serve warm.