Heat the oil and the lemongrass over low heat and leave to infuse off the heat for a few hours.
Preheat the oven the oven to 200°C.
Place beetroot on foil on roasting tray, drizzle with a bit of the lemongrass oil.
Season with salt, wrap and cook for 1 hour until tender. Cool, peel and cut into wedges.
Reheat the remaining oil, add mustard seed and allow to crackle over low heat. Allow oil to cool then add the remaining ingredients, mix well and toss over the roasted beetroot.