Preheat your oven to 400°F (200°C) and line a large baking sheet with parchment paper.
Press the extra firm tofu to remove excess moisture, then cut it into 1/2-inch cubes.
Rinse and drain the chickpeas, patting them very dry with a clean towel to ensure they crisp up in the oven.
In a large mixing bowl, combine the tofu cubes, chickpeas, broccoli florets, and cauliflower florets.
Drizzle with olive oil and sprinkle with sea salt, black pepper, and garlic powder, tossing until everything is 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 vegetables are tender and the tofu is golden brown.
While the bowl components roast, whisk together the tahini, lemon juice, nutritional yeast, and water in a small bowl until the dressing is smooth and pourable.
Transfer the roasted vegetables, tofu, and chickpeas to a serving bowl, drizzle with the lemon-tahini sauce, and garnish with hemp hearts.