Preheat the oven to 400 degrees. Toss the tomatoes, mushrooms, zucchini, bell pepper, red onion, and whole garlic cloves with olive oil, balsamic vinegar, Italian seasoning, salt, and pepper. Spray a baking sheet with cooking spray. Spread out the vegetables and roast for 20 minutes.
Meanwhile, prepare the couscous. Bring the vegetable broth to a boil. Stir in the couscous and cover. Remove from heat and let sit for 10 minutes. Fluff with fork. If there is any extra liquid, drain it off. If the package directions differ from these, follow package directions since there are many types of couscous.
To serve: Add the vegetables and all the juices from the baking sheet to the couscous. Stir in the fresh parsley and basil. Season with salt and pepper. If desired, serve with fresh lemon juice and an extra drizzle of olive oil and balsamic vinegar.