Rinse the quinoa thoroughly under cold water using a fine-mesh sieve. In a medium saucepan, heat 1 tablespoon olive oil over medium heat. Add the minced garlic and sauté for 30 seconds until fragrant.
Add the rinsed quinoa and cumin, stirring to toast for about 1 minute. Pour in the vegetable broth, bring to a boil, then reduce heat to low. Cover and simmer for 15-18 minutes until the liquid is absorbed and the quinoa is fluffy.
Preheat your oven to 425°F (220°C) and line a large baking sheet with parchment paper. In a large bowl, combine the diced sweet potato, bell peppers, zucchini, and red onion.
Drizzle vegetables with olive oil and sprinkle with smoked paprika, chili powder, cayenne pepper, salt, and black pepper. Toss until all vegetables are evenly coated with oil and spices.
Spread the seasoned vegetables in a single layer on the prepared baking sheet. Avoid overcrowding to ensure proper caramelization—use two sheets if necessary. Roast in the preheated oven for 25-30 minutes, stirring halfway through, until the vegetables are tender and developing golden brown edges.
While everything is cooking, whisk together tahini, water, lemon juice, maple syrup, sriracha, and salt in a small bowl until smooth and pourable. If the mixture is too thick, add water one teaspoon at a time until you reach your desired consistency.
When the quinoa has absorbed all the liquid, remove from heat and let sit covered for 5 minutes. Fluff with a fork, then stir in the lime juice.
Divide the cooked quinoa among serving bowls. Top with the roasted vegetables, arranging them in sections for visual appeal. Drizzle with the spicy tahini sauce and garnish with your choice of toppings: toasted pumpkin seeds, fresh cilantro, avocado slices, and lime wedges.