Preheat your oven to 400°F and line a large baking sheet with parchment paper.
Drain the tofu and press it firmly between paper towels to remove as much moisture as possible, then cut into 1-inch cubes.
Peel and cube the sweet potato into 0.5-inch pieces and chop the broccoli into bite-sized florets.
In a large bowl, toss the tofu, sweet potato, and broccoli with the olive oil, sea salt, black pepper, and garlic powder until evenly coated.
Sprinkle the nutritional yeast over the tofu and vegetables, tossing again to ensure the yeast adheres to the tofu for a crispy exterior.
Spread the mixture in a single layer on the prepared baking sheet and roast for 25 to 30 minutes, flipping halfway through, until the tofu is golden and the potatoes are tender.
While the vegetables roast, whisk together the tahini, lemon juice, and water in a small bowl until the dressing is smooth and pourable.
Transfer the roasted tofu and vegetables to a bowl and drizzle the lemon-tahini dressing over the top before serving.