For yogurt:
Combine cilantro, lime juice, and salt in processor; blend to coarse puree. Transfer to bowl; mix in yogurt and sour cream. Season with pepper.

For vegetables:
Preheat oven to 400°F. Spray 2 large baking sheets with nonstick spray. Mound eggplant cubes on 1 sheet; drizzle with 4 tablespoons oil. Sprinkle with salt and pepper; toss to coat. Spread out evenly. Mound zucchini on second sheet; drizzle with remaining 2 tablespoons oil. Sprinkle with salt and pepper; toss to coat. Spread out evenly. Roast eggplant and zucchini until golden and tender, turning occasionally with spatula, about 25 minutes for zucchini and 50 minutes for eggplant. Transfer vegetables to bowl and cool.

Meanwhile, char peppers directly over gas flame or in broiler until blackened on all sides. Enclose in paper bag; let stand 10 minutes. Peel and seed peppers. Cut 2peppers into 1-inch pieces.

For couscous:
Heat 1 tablespoon oil in heavy large saucepan over medium-high heat. Add onion; sauté until soft, about 6 minutes. Mix in curry powder; stir 1 minute. Add 3 cups water; bring to simmer. Cover; reduce heat to medium-low and simmer curry water 10 minutes.

Heat remaining 1 tablespoon oil in heavy large pot. Add couscous and stir constantly until color darkens and couscous is toasted, about 3 minutes. Mix in hot curry water. Turn off heat, cover pot, and let stand until couscous is tender and curry water is absorbed, about 10 minutes. Fluff couscous with fork to separate grains. Mix in cashews and currants and cool completely. Mix in eggplant, zucchini, and bell pepper pieces. Season salad to taste with salt and pepper.

Mound salad on large platter. Serve with cilantro yogurt and chutney.