Set the oven to 190°C.
Wash and wipe the sweet potatoes, then cut them into wedges. Put them on a baking tray.
Smash the garlic slightly with a tenderiser and scatter these around the sweet potatoes. Scatter the rosemary leaves on top, then pour over a Tbsp of olive oil and rub in the sweet potato wedges. Cut an insertion into the chillis (if used), then tuck these between the wedges.
Season with salt and pepper. Roast in the oven for 25 minutes, until brown and soft, turning them once or twice.
Serve them warm.