Preheat your oven to 400°F and line a large baking sheet with parchment paper for easy cleanup.
Cut the chicken breast into 1-inch bite-sized pieces and chop the cauliflower, bell pepper, and onion into uniform chunks.
In a large mixing bowl, whisk together the olive oil, harissa paste, lemon juice, sea salt, and black pepper until well combined.
Add the chicken and chopped vegetables to the bowl and toss thoroughly until every piece is coated in the spicy harissa glaze.
Spread the mixture in a single layer on the prepared baking sheet, ensuring there is space between pieces to allow for proper roasting.
Roast in the oven for 20-25 minutes, or until the chicken is cooked through and the vegetables have developed slightly charred, caramelized edges.
While the tray is roasting, lightly toast the pine nuts in a small dry skillet over medium heat for 2-3 minutes until golden and fragrant.
Remove the tray from the oven and garnish with the toasted pine nuts and freshly chopped parsley before serving hot.