Preheat your oven to 400°F and line a large rimmed baking sheet with parchment paper.
Cut the chicken breast into 1-inch bite-sized pieces and break the cauliflower into small, uniform florets.
Place the chicken and cauliflower on the prepared baking sheet, then drizzle with olive oil and sprinkle with smoked paprika, sea salt, and black pepper.
Toss everything together until the ingredients are evenly coated, then spread them out into a single layer.
Roast for 20 to 25 minutes, tossing halfway through, until the chicken is cooked through and the cauliflower edges are caramelized.
While the tray is roasting, whisk the tahini, lemon juice, minced garlic, and water in a small bowl until the sauce is smooth and creamy.
Remove the sheet pan from the oven and transfer the roasted chicken and cauliflower to a serving bowl.
Drizzle the warm tahini sauce over the top and serve immediately.