Preheat oven to 400°F and line a baking sheet with parchment paper.
Cut the tempeh into bite-sized cubes and steam for 10 minutes to remove any bitterness.
In a large mixing bowl, whisk together the olive oil, lemon juice, dried oregano, garlic powder, sea salt, and black pepper.
Add the steamed tempeh cubes, broccoli florets, and sliced red bell pepper to the bowl, tossing until everything is well coated.
Spread the mixture in a single layer on the prepared baking sheet.
Roast for 20 to 25 minutes, flipping the ingredients halfway through, until the tempeh is golden brown and the vegetables are tender.
Remove from the oven and sprinkle the nutritional yeast over the top before serving.