Preheat oven to 400°F (200°C) and line a large baking sheet with parchment paper.
Press the extra firm tofu between paper towels to remove excess moisture, then cut into 1/2-inch cubes.
In a large bowl, toss the tofu cubes, chickpeas, and cauliflower florets with olive oil, sea salt, black pepper, and garlic powder until evenly coated.
Spread the mixture in a single layer on the prepared baking sheet and roast for 25-30 minutes, tossing halfway through, until the tofu is golden and the vegetables are tender.
While roasting, prepare the dressing by whisking together the tahini, lemon juice, nutritional yeast, and water in a small bowl until smooth and creamy.
Assemble the bowl by placing the fresh spinach at the base, topping with the roasted tofu and vegetable mixture, and sprinkling with hemp seeds.
Drizzle the lemon-tahini dressing over the top and serve immediately.