Preheat your oven to 400°F (200°C) and line a large rimmed baking sheet with parchment paper.
Cut the chicken breast into 1-inch cubes and ensure the cauliflower is broken into small, uniform florets.
In a large mixing bowl, combine the chicken, cauliflower, olive oil, sea salt, black pepper, garlic powder, and smoked paprika.
Toss the ingredients thoroughly until every piece is evenly coated in the oil and spices.
Spread the mixture across the prepared baking sheet in a single layer, making sure not to overcrowd the pan so the vegetables roast rather than steam.
Roast for 20 to 25 minutes, tossing halfway through, until the chicken is cooked through and the cauliflower edges are caramelized and tender.
While the tray is in the oven, whisk together the tahini, lemon juice, and warm water in a small bowl until the sauce reaches a smooth, pourable consistency.
Remove the tray from the oven and transfer the roasted chicken and cauliflower to a serving bowl.
Drizzle the velvety tahini sauce over the top and garnish with freshly chopped parsley before serving hot serving.