Preheat your oven to 400°F and line a large rimmed baking sheet with parchment paper for easy cleanup.
Cut the tempeh into 1-inch cubes and chop the broccoli and red bell pepper into uniform, bite-sized pieces.
In a large mixing bowl, whisk together the extra virgin olive oil, fresh lemon juice, tamari, dried oregano, garlic powder, sea salt, and black pepper.
Add the tempeh cubes to the bowl first, tossing well to ensure the marinade penetrates the plant-based protein.
Add the broccoli florets and bell peppers to the bowl, tossing gently until all components are evenly coated with the herb mixture.
Spread the tempeh and vegetables in a single layer on the prepared baking sheet, leaving enough space between them to ensure they roast rather than steam.
Roast in the center of the oven for 20-25 minutes, tossing halfway through, until the tempeh is golden-brown and the vegetables are tender with charred edges.
Remove from the oven and immediately sprinkle with nutritional yeast to add a savory, cheesy finish before serving.