Preheat the oven to 400°F and line a large baking sheet with parchment paper.
Drain and rinse the chickpeas, then pat them completely dry with a clean kitchen towel to ensure they crisp up.
Cut the tempeh into 1/2-inch cubes and place them on the baking sheet along with the chickpeas and broccoli florets.
Drizzle the olive oil over the ingredients on the sheet, sprinkle with garlic powder, sea salt, and black pepper, and toss to coat evenly.
Roast for 20-25 minutes, tossing halfway through, until the tempeh is golden and the chickpeas are crisp.
In a small bowl, whisk together the tahini and lemon juice until smooth, adding a splash of water if needed to reach a pourable consistency.
Transfer the roasted mixture to a bowl, drizzle with the lemon-tahini dressing, and top with hemp seeds before serving.