Heat oil in a large pot over medium-high heat; saute onion until golden. Pour in vegetable broth and bring to a boil. Stir in carrots, turnips and sweet potato. Reduce heat to medium and simmer 15 minutes.
Reduce heat to low and add zucchini and red bell pepper. Simmer for 20 minutes.
Stir in garbanzo beans, tomato sauce, cinnamon, turmeric, saffron and curry powder. Simmer until heated through.
Meanwhile, bring 2 1/2 cups water to a boil. Stir in couscous, cover and remove from heat. Let stand 5 to 7 minutes. Fluff with a fork and serve with vegetables on top.