In a large mixing bowl combine quinoa, roasted sweet potatoes, corn, bell pepper, black beans, red onion, cilantro and avocado. Add 1/4 cup olive oil, lime juice, chili powder, cayenne, cumin, black pepper and sea salt. Gently toss the salad to combine. Taste and adjust the seasoning, if necessary. Serve salad right away or chill in the fridge a few hours before serving. Add a sprinkle of queso fresco or feta cheese when serving, if desired.