Place sweet potatoes cut-side down on a baking tray. Coat with 1 teaspoon oil and a pinch of salt.
Roast potatoes in the preheated oven until tender, turning halfway through, about 25 minutes.
Heat remaining 2 teaspoons oil in a heavy pot over medium-high heat. Add onion; cook and stir until starting to brown, about 5 minutes. Add tomatoes, garlic, red curry paste, ginger and lemon zest. Cook, stirring frequently, until fragrant, about 3 minutes.
Stir chickpeas into the pot. Increase heat to high; cook until chickpeas start to turn golden and are coated with the onion mixture. Pour in lemon juice, coconut milk and 1 teaspoon salt. Heat until simmering; reduce heat and cook until flavours combine, about 10 minutes. Stir in kale, 1 handful at a time, until wilted, about 5 minutes.
Serve chickpea mixture over roasted sweet potatoes.