In a mixing bowl, combine the harissa paste, lemon zest, lemon juice, minced garlic, olive oil, salt, and pepper. Whisk together until smooth and well blended.
Pat the whole chicken dry with paper towels. Loosen the skin over the breasts and thighs. Rub about two-thirds of the harissa marinade under the skin and over the chicken surface.
In a separate bowl, toss the halved baby potatoes with the remaining marinade until well coated.
Place the chicken breast-side up in the center of your roasting pan or oven-safe skillet. Scatter the marinated potatoes around the chicken evenly.
Preheat oven to 425°F (220°C). Roast chicken and potatoes for 1 hour to 1 hour 15 minutes, until chicken reaches 165°F (75°C) and potatoes are tender and golden. Halfway through, baste chicken and toss potatoes.
Remove from oven and let chicken rest for 10-15 minutes. Sprinkle chopped fresh parsley over chicken and potatoes. Carve and serve.
