My favorite sweet potato/apple dish uses apple slices alternating with peeled, raw sweet potato slices in one layer in a baking dish, drizzled with vinegar and melted butter. My ratio is one small to medium red-skinned sweet potato and one golden delicious apple with 1 tablespoon each of balsamic vinegar and butter. A 9 x 13 dish holds 4 times that. Bake uncovered until tender, perhaps 45 minutes at around 350 degrees. The vinegar brings out the natural sweetness of the apples and sweet potatoes.
I'd bet that replacing the vinegar with Amaretto, perhaps doubled, would be delicious.