Preheat the oven to 400°F (200°C). Spread the diced sweet potatoes on a baking sheet, drizzle with olive oil, and season with salt and pepper. Roast for 25-30 minutes, or until tender and slightly caramelized, stirring halfway through.

While the sweet potatoes are roasting, cook the quinoa. In a medium saucepan, combine the rinsed quinoa and vegetable broth (or water). Bring to a boil, then reduce heat to low, cover, and simmer for 15 minutes or until the quinoa is fluffy and the liquid is absorbed. Remove from heat and let it sit covered for 5 minutes before fluffing with a fork.

In a large bowl, combine the cooked quinoa, roasted sweet potatoes, red bell pepper, black beans, corn, red onion, and cilantro.

In a small bowl, whisk together the lime juice, olive oil, cumin, salt, and pepper. Pour the dressing over the salad and toss gently to combine.

Just before serving, add the diced avocado and toss lightly to avoid mashing.