Wash and peel the sweet potatoes.
Cut the sweet potatoes into chunks (this means it is quicker to boil and in the future more surface area for the roasted potatoes to crisp up).
Boil a pot of water and lightly salt the water and add 1 tablespoon of rosemary to the water - add in the sweet potato chunks and parboil them for 15-20 minutes.
Whilst the sweet potatoes are parboiling, add oil to your baking trays. I added 1 tablespoon of oil per tray. This helps to make the sweet potatoes extra crispy.
Once parboiled, drain the sweet potatoes from the water and add them to the oiled trays.
Next, lightly coat the sweet potatoes with 2 tablespoons, 1 tablespoon of rosemary and thyme and half a tablespoon of pepper. Make sure all the seasoning is evenly distributed on all the sweet potatoes and on all the surface of the sweet potatoes.
Place the sweet potato trays in the oven for 1 hour at 200°C fan with a tin foil covering over the top (this enables the sweet potato to cook but prevents burning).
Take the sweet potato tray out of the oven. Using a spoon using the juices, re-coat the sweet potatoes with the juices in the tray, so every surface of the potatoes is covered.
Place the sweet potatoes back in the oven for 30 minutes at the same temperature (or slightly higher to ensure they are crispy) without the tin foil to let them roast and crisp.
Finally, take the crispy roasted sweet potatoes out of the oven either at 30 minutes or whenever the roast potatoes are crispy enough to your liking (make sure to monitor them throughout).
