Place the kumara into a large pot and cover with water. Bring to a boil over high heat, then reduce heat to medium-low, cover, and simmer until tender, about 15 minutes. Drain and allow to steam dry for a minute or two. Allow to cool, then slice each kumara into wedges. Arrange wedges on a baking tray.
Preheat an oven to 200 degrees C.
Brush the kumara wedges with olive oil, and lightly season with salt and pepper. Combine sea salt, lime zest, chilli powder, paprika, and chilli flakes in a small bowl.
Bake in the preheated oven until golden brown on all sides, about 20 minutes. Plate and sprinkle with the seasoning mixture and coriander immediately.