You can, but if you want to freeze them before they're cooked you should blanch the potatoes first to prevent mushiness when defrosting. Do this by simply placing the sweet potato medallions for 3-4 minutes in a pot of water that's been boiled and removed from the heat, transferring to a bowl of ice water to cool, and placing in airtight bags or plastic containers. They'll last in the freezer for around 6 months.