Toss cauliflower, mushrooms and bell pepper with 2 tablespoons oil. Sprinkle with thyme and cumin. Toss until evenly coated.
Spread in single layer on baking sheet. Roast in preheated 450-degree oven 15-20 minutes or until cauliflower is golden brown, stirring occasionally.
Meanwhile, heat remaining 2 teaspoons oil in large saucepan on medium-high heat. Add onions; cook and stir 5 minutes or until softened. Add vegetable mixture, broth and pepper. Bring to boil. Reduce heat to low; simmer 10 minutes or until cauliflower is tender, stirring occasionally.
Ladle into soup bowls to serve.
Nutrition information per 1-cup serving: 105 calories, fat 5 grams, protein 3 grams, carbohydrates 12 grams, sodium 304 mg, fiber 3 grams