Heat oven to 375 degrees F. In a small bowl, stir together lemon juice, basil, parsley, 1/2 teaspoon of the salt and 1/2 teaspoon of the pepper. Slowly whisk in olive oil; set aside.
In a large bowl, combine tomatoes, squash, potatoes and carrots. Sprinkle mixture with remaining 1 teaspoon salt and 1/2 teaspoon pepper. Drizzle with prepared lemon dressing and stir well to combine.
Pour vegetable mixture into a 13 x 9 x 2-inch baking dish and cover with foil. Bake at 375 degrees F for 35 minutes. Remove foil and continue to bake another 15 minutes or until vegetables are tender.
When there is 10 minutes bake time remaining, prepare couscous according to package directions. Remove vegetable mixture from oven and carefully stir in couscous. Serve immediately.