Preheat your oven to 400°F (200°C). Wash and chop the mixed vegetables into bite-sized pieces. Toss the vegetables with olive oil, salt, black pepper, garlic powder, and smoked paprika until evenly coated.

Spread the seasoned vegetables on a baking sheet lined with parchment paper. Roast for 25-30 minutes, flipping halfway through until tender and caramelized.

While the vegetables roast, rinse the lentils under cold water. Boil them in salted water, then reduce to a simmer and cook for about 20 minutes until tender. Drain and let cool.

Combine the cooled roasted vegetables and lentils in a large bowl. Squeeze lemon juice over the mixture and toss gently.

Fold in the fresh parsley and feta cheese, if using. Let the salad sit for 10 minutes before serving.