Preheat your oven to 400°F (200°C) and line a large baking sheet with parchment paper.
Cut the tempeh into 1/2-inch cubes and place them in a mixing bowl; toss with the coconut aminos, nutritional yeast, garlic powder, sea salt, and black pepper until every piece is evenly coated.
Spread the seasoned tempeh, broccoli florets, and cauliflower florets in a single layer on the prepared baking sheet.
Roast in the oven for 20 to 25 minutes, tossing halfway through, until the vegetables are tender-crisp and the tempeh is golden and firm.
While the vegetables roast, prepare the dressing by whisking the tahini and lemon juice in a small bowl, adding a teaspoon of warm water at a time until it reaches a smooth, pourable consistency.
Place the fresh spinach in a wide serving bowl and top with the roasted vegetable and tempeh mixture, followed by the shelled edamame.
Drizzle the creamy lemon-tahini dressing over the entire bowl and serve immediately while the roasted ingredients are still warm.