Preheat oven to 400°F (200°C) and line a large baking sheet with parchment paper.
Press the extra firm tofu for 15 minutes to remove excess moisture, then cut into 1-inch cubes.
Peel and chop the sweet potato, carrots, and parsnips into uniform 1-inch pieces.
In a large bowl, whisk together the olive oil, minced garlic, rosemary, thyme, sea salt, and black pepper.
Add the tofu cubes and root vegetables to the bowl, tossing thoroughly to ensure everything is evenly coated in the herb oil.
Spread the mixture in a single layer on the prepared baking sheet and roast for 25-30 minutes, flipping halfway through, until the vegetables are tender and tofu is golden.
While roasting, whisk together the non-fat Greek yogurt and lemon juice in a small bowl until smooth.
Plate the roasted vegetable and tofu mixture, drizzle with the lemon-yogurt sauce, and sprinkle with hemp seeds for an extra protein boost.