Preheat oven to 425°. Boil the cashews in 4 cups of water for 15 minutes, or until softened.
In a small bowl, stir together 1 tablespoon olive oil, the tahini, lemon juice, drained cashews and 2 tablespoons of water. Stir in additional water, 1 teaspoon at a time, until sauce is desired consistency. Stir in raisins.
In a medium bowl, combine 1 tablespoon olive oil, the harissa, garlic, 1/2 teaspoon salt and cinnamon. Add chickpeas, bell pepper and onion; stir to coat. Spread on a lined baking pan.
Place a second lined baking pan in the oven to preheat 5 minutes. Brush cut sides of sweet potatoes with remaining 1 tablespoon olive oil and sprinkle with remaining 1/2 teaspoon salt. Place potatoes, cut sides down, on hot baking pan. Roast until tender, 30 to 35 minutes.
After potatoes have baked for 15 minutes, add the pan with chickpeas to oven; roast until crisp, stirring once, 15 to 20 minutes. To serve, spoon chickpea mixture over potatoes. Drizzle with tahini sauce and sprinkle with mint, parsley & lemon zest.