Preheat the oven to 400°F and line a baking sheet with parchment paper.
Transfer the chopped broccoli, sweet potatoes, and chickpeas to the prepared baking sheet. Season with half of the lemon juice, Italian seasoning, and nutritional yeast. Bake for 30–35 minutes, or until the vegetables are very tender and the chickpeas are crispy.
While the vegetables are roasting, add the quinoa and broth to a medium pot with a tight-fitting lid. Bring to a boil, cover, and reduce heat to low. Simmer for 15–20 minutes, or until the liquid is absorbed and the quinoa is tender. Stir occasionally to prevent sticking. Once cooked, remove from heat, fluff with a fork, and set aside.
While the quinoa cooks, combine the tahini, warm water, dates, and remaining lemon juice in a small blender. Blend until smooth.
To assemble, divide the quinoa and roasted vegetables between bowls. Drizzle with tahini sauce and top with pumpkin seeds (optional).