Preheat oven to 400°F (200°C) and line a baking sheet with parchment paper.
Cut the tempeh into bite-sized cubes and chop the broccoli and bell pepper into uniform pieces.
In a large bowl, whisk together the olive oil, lemon juice, dried oregano, garlic powder, sea salt, and black pepper.
Add the tempeh, broccoli, and bell peppers to the bowl, tossing thoroughly to ensure every piece is coated in the herb mixture.
Spread the mixture in a single layer on the prepared baking sheet.
Roast for 20-25 minutes, tossing halfway through, until the vegetables are tender and the tempeh is slightly golden.
Remove from the oven and immediately sprinkle with nutritional yeast, tossing once more before serving warm.