When heating up the oven to roast sweet potatoes, go ahead and roast as many as you can fit (without overcrowding) on your roasting pan, and if your oven is big enough, roast two pans full at the same time. Eat what you want; freeze the rest and store in ziplock bags. Remove from the freezer the morning you want to eat them; they'll easily reheat in a fraction of the time it takes to bake.