Preheat oven to 425°F and place a rack in the middle.
Line a baking sheet with parchment paper and spread sweet potato and white potato cubes on a single layer. Drizzle with 1 tablespoon of olive oil and sprinkle with salt.
Roast for 15 minutes or until tender and gold, tossing halfway through.
Remove from the oven and set aside.
Heat the remaining 2 tablespoons of olive oil in a large saucepan over medium-high heat.
Add onion and a pinch of salt and sauté until translucent, about 6 minutes.
Add garlic and sauté for 1 more minute.
Add ginger and spices and sauté for 30 seconds, until fragrant.
Add diced tomatoes. Bring to a boil, lower to a simmer, and cook for 15 minutes.
Remove from the heat and puree with an immersion blender until smooth, or alternately puree in a blender (this is optional but makes the gravy much creamier.)
Add roasted sweet potatoes potatoes, chickpeas, and sweet peas. Stir in coconut milk and cook for further 5 minutes.
In the meantime in a small bowl whisk arrowroot (or cornstarch) with 2 tablespoons of water. Stir in the sweet potato mixture and cook for 5 more minutes or until the gravy has thickened.
Take a taste and adjust seasoning if needed.
Remove from the heat, sprinkle with chopped fresh cilantro and serve.
DONE!
