Preheat oven to 450 degrees F. Make rub: combine paprika, cumin and pepper.
On a large rimmed baking sheet, toss 2 tablespoons olive oil, one-third of rub, and ½ teaspoon salt with potatoes, carrots, brussels sprouts, and onion. Roast for 10 minutes
On another baking sheet, toss 2 teaspoons olive oil and one-third of rub with mushrooms, asparagus, and green beans. Push to one side of pan. On other side, arrange chicken pieces. Sprinkle with remaining rub. Season veggies and protein with 1/2 teaspoon salt. Roast both pans 20 to 35 minutes or until chicken is cooked and all veggies are softened (transfer chicken from pan to platter if cooked before veggies are tender). To serve, garnish with parsley and squeeze of lemon.