Preheat the oven to 425°F (220°C). Line a large baking sheet with parchment paper.
In a medium bowl, toss the drained chickpeas with 1/2 tablespoon olive oil, smoked paprika, ground cumin, garlic powder, cayenne pepper, and 1/4 teaspoon salt until evenly coated.
Spread the chickpeas in a single layer on one side of the prepared baking sheet.
In a large bowl, combine broccoli florets, red bell pepper strips, and diced sweet potato. Drizzle with 1 tablespoon olive oil and sprinkle with 1/4 teaspoon salt. Toss to coat evenly.
Spread the vegetables in a single layer on the other side of the baking sheet.
Roast chickpeas and vegetables in the preheated oven for 25 to 30 minutes, stirring the vegetables halfway through cooking, until the chickpeas are crispy and the vegetables are tender and slightly caramelized.
While the chickpeas and vegetables roast, prepare the lemon-tahini dressing. In a small bowl, whisk together lemon juice, tahini, water, maple syrup, and a pinch of black pepper until smooth and creamy. Add more water if needed to reach desired consistency.
Remove the baking sheet from the oven. Transfer roasted chickpeas and vegetables to serving plates or bowls.
Drizzle the lemon-tahini dressing over the roasted chickpeas and vegetables before serving.