Preheat your oven to 400°F (200°C) and line a large baking sheet with parchment paper.
Peel and dice the sweet potato into half-inch cubes, and break the broccoli and cauliflower into uniform bite-sized florets.
Slice the chicken breast into thin, even strips to ensure quick and consistent cooking.
Place the chicken and all the vegetables onto the baking sheet, then drizzle with olive oil and sprinkle with sea salt, black pepper, garlic powder, and smoked paprika.
Toss everything thoroughly with your hands to coat each piece evenly in the oil and spices.
Roast in the center of the oven for 20 to 25 minutes, or until the chicken is cooked through and the vegetables have developed tender, golden-brown edges.
While roasting, whisk the tahini and lemon juice in a small bowl, adding a teaspoon of warm water at a time until it reaches a smooth, pourable consistency.
Transfer the roasted chicken and vegetables to a serving bowl and finish by drizzling the creamy tahini dressing over the top.