Heat oven to 220C/fan 200C/gas 7. In a bowl, mix together the oil and spices. Add the vegetables and mix well. Spread over a heavy baking sheet, then roast for 30 mins until tender.
Spoon into a food processor or liquidiser with half the stock and process until smooth. Pour into a pan with the remaining stock, season, then heat until barely simmering. Remove from the heat and stir in the lemon juice. Garnish with cumin seeds.
Recipe from Good Food Vegetarian Christmas magazine, December 2006