Preheat your oven to 400°F and line a large rimmed baking sheet with parchment paper for easy cleanup.
Cut the tempeh and Yukon gold potatoes into uniform 1/2-inch cubes and break the broccoli into small, bite-sized florets.
In a large mixing bowl, whisk together the avocado oil, coconut aminos, garlic powder, smoked paprika, sea salt, and black pepper.
Add the tempeh, potato cubes, and broccoli florets to the bowl and toss thoroughly until every piece is well-coated with the marinade.
Spread the mixture in a single layer on the prepared baking sheet, ensuring the pieces aren't overcrowded so they roast rather than steam.
Roast for 20-25 minutes, tossing the ingredients halfway through, until the potatoes are fork-tender and the tempeh is golden and crisp.
Place the warm cooked buckwheat in a serving bowl, top with the roasted tempeh and vegetable mixture, and finish with a sprinkle of nutritional yeast and hemp seeds.