Preheat the oven to 400°F (200°C). Toss cherry tomatoes, diced zucchini, and red bell pepper with 1 tablespoon of olive oil, salt, and pepper. Spread evenly on a baking sheet and roast for 15-20 minutes until vegetables are tender and slightly caramelized.
While vegetables roast, bring 2 cups of water to a boil in a large pot. Add pearl couscous and a pinch of salt, then reduce heat to low and cover. Simmer for 10-12 minutes until couscous is tender and fluffy, then drain any excess water and transfer to a large mixing bowl.
Once the vegetables are done roasting, add them to the bowl with cooked couscous. Pour in juice of one lemon, remaining 2 tablespoons of olive oil, and ground sumac. Toss gently to combine, ensuring the grains are coated with the dressing and vegetables are evenly distributed.
Stir in chopped parsley and taste, then adjust seasoning with additional salt, pepper, or lemon juice as needed. The salad should be slightly chewy with bursts of flavor from the sumac and fresh herbs, and colorful from the roasted vegetables.
Serve the salad at room temperature or chilled, garnished with extra herbs if desired. The dish showcases a vibrant combination of textures, from tender grains and roasted vegetables to crunchy herbs and tangy dressing.
