Place chicken on cookie sheet and rub with 1 tablespoon olive oil. Season inside and outside of chicken with 2 teaspoons salt and 1/2 teaspoon pepper. Place 1/2 red onion, lemon and 2 sprigs rosemary inside chicken cavity. Place in 4 quart oval pan, breast side up.
Mince remaining rosemary. Thinly slice remaining red onion. In large bowl, combine potatoes, carrots, red onion, rosemary, garlic and remaining salt, pepper and oil; toss to coat. Place vegetables around chicken in pan.
Bake 60-65 minutes or until instant thermometer inserted into the thickest part of the thigh reads 160-165°F. Remove to cooling grid; cover with aluminum foil 5-10 minutes. Serve warm.