01 - Preheat the oven to 425°F (220°C) and line a large baking sheet with parchment paper.
02 - Combine harissa paste, olive oil, smoked paprika, ground cumin, salt, black pepper, and minced garlic in a large bowl. Mix thoroughly.
03 - Add chicken thighs to the marinade and toss until evenly coated. Let marinate for at least 10 minutes, or refrigerate up to 2 hours for enhanced flavor.
04 - Place sweet potato cubes and red onion wedges onto the prepared baking sheet. Drizzle lightly with olive oil, season with salt and pepper, and toss to coat evenly.
05 - Arrange the marinated chicken thighs on top of the sweet potatoes and onions in a single layer.
06 - Roast in the preheated oven for 40 to 45 minutes, or until chicken reaches an internal temperature of 165°F (75°C) and sweet potatoes are tender and caramelized.
07 - Transfer to serving plates, garnish with chopped cilantro or parsley, and serve alongside lemon wedges.