Pre-heat oven to 230°C. Peel the sweet potatoes and slice them into fry-shaped pieces, about 1cm wide and 8cm long. Make sure to cut them all the same size, so they cook evenly.
In a baking tray, coat the sweet potatoes lightly with olive oil, Roast Vegetable Salt and cayenne, making sure the fries form a single layer.
Bake for 25-30 minutes, flipping the fries occasionally to achieve a uniform golden brown colour and crispiness.
To serve
Sprinkle with a little more salt if necessary and serve immediately with cold aioli.