Preheat the oven to 220°C (200°C fan), Gas Mark 7. Line a large baking tray with baking paper.
Place the sweet potato slices on the lined tray. Drizzle the slices with the olive oil, sprinkle over the ras el hanout and add a generous amount of salt, then use your hands to rub the mixture evenly all over them. Spread out in a single layer and roast for 30 minutes or until cooked through.
Meanwhile, for the herb oil, put the herbs, lemon juice, olive oil (enough to enable the mixture to spin) and some salt and pepper into a blender and blitz until smooth.
Mix the yoghurt and tahini together in a small bowl and season well with salt and pepper.
Remove the sweet potatoes from the oven and transfer to a platter. Pour over the tahini yoghurt followed by the herb oil. Scatter with the pine nuts and pomegranate seeds and serve.