Preheat your oven to 400°F and line a large baking sheet with parchment paper.
In a large mixing bowl, whisk together the olive oil and harissa paste until smooth.
Add the chicken breast strips, cauliflower florets, sliced zucchini, and chopped red bell pepper to the bowl.
Toss everything thoroughly until the chicken and vegetables are evenly coated in the harissa mixture.
Spread the mixture onto the prepared baking sheet in a single layer, ensuring the pieces are not overlapping.
Season the tray evenly with sea salt and black pepper.
Roast for 20 to 25 minutes, or until the chicken is cooked through and the vegetables are tender with slightly charred edges.
While the chicken roasts, stir together the Greek yogurt and lemon juice in a small bowl to create a cooling sauce.
Remove the tray from the oven and serve immediately with a dollop of the lemon-yogurt sauce and a garnish of fresh parsley.