Toss the sweet potato with the oil and spread out on a large baking tray lined with baking parchment. Season and roast for about 25 minutes, until the potato is soft. Remove from the oven and set aside to cool.
In a food processor, pulse the peas with the ground coriander, cumin, parsley and fresh coriander until finely chopped. Add the potato and pulse until combined. Shape the mixture into 16 golfball–sized patties and arrange on a baking tray lined with baking parchment.
Bake in the oven for 15 to 20 minutes, until golden. Remove from the oven and leave to cool for 5 minutes, before lifting with a spatula.
Meanwhile, combine all the sauce ingredients in a bowl with some seasoning. Chill until needed. Serve the falafels in the tortilla wraps with lettuce leaves, a handful of shredded carrot and a drizzle of the yoghurt sauce.