How to Make It
Preheat oven to 375°F. Stir together first 5 ingredients, 4 teaspoons of the salt, and 2 teaspoons of the pepper. Remove necks and giblets from chickens, and reserve for another use. Pat chickens dry.
Sprinkle 1 teaspoon brown sugar mixture inside cavity of each chicken. Rub 1 tablespoon olive oil into skin of each chicken. Sprinkle evenly with remaining brown sugar mixture; rub into skin. Tuck wing tips under.
Toss together potatoes, carrots, remaining 1 tablespoon olive oil, remaining 1 teaspoon salt, and remaining 1/2 teaspoon pepper. Spread potato mixture in a single layer in a 17- x 12-inch rimmed baking sheet. Place chickens, breast side up, facing in opposite directions (for even browning), on top of potato mixture.
Bake in preheated oven until a meat thermometer inserted in thickest portion of thigh registers 165°F, 1 hour to 1 hour and 15 minutes. Cover and let stand 10 minutes before slicing. Stir parsley into vegetables.
Toss together 2 heads chopped romaine lettuce; 1 cup thinly sliced cucumber; 2 cups halved cherry tomatoes; and 1 avocado, cut into wedges. Top with sliced leftover BBQ Rub Roasted Chicken. Serve with your favorite buttermilk dressing.