Preheat the oven to 400°F (200°C).
In a large baking dish, toss the diced bell peppers, zucchini, and cherry tomatoes with olive oil, salt, and pepper.
Roast in the oven for 20-25 minutes until the vegetables are tender and slightly charred.
In a large bowl, combine the cooked quinoa, roasted vegetables, parsley, lemon juice, and olive oil.
Season with salt and pepper to taste and toss well to combine.
Serve at room temperature or chilled for a refreshing salad.