Preheat oven to 400 degrees F. Lightly oil a 9 x 13 baking dish or coat with nonstick spray.
In a small saucepan over medium heat, combine orange juice, brown sugar, butter, 1 teaspoon salt and 1/4 teaspoon pepper until butter has melted, about 4 minutes. Remove from heat; stir in vanilla, cinnamon, nutmeg and rosemary.
Place potatoes into the prepared baking dish; stir in orange juice mixture.
Place into oven and bake, covered, for 40 minutes. Uncover; continue to bake for an additional 20 minutes, basting every 7-8 minutes until potatoes are tender and orange juice mixture is syrupy. Season with salt and pepper, to taste.
Serve immediately, garnished with pecans, if desired.
Notes
Use firm potatoes. When purchasing sweet potatoes, look for small to medium evenly shaped potatoes that are firm with smooth and taut skin.
Cut in uniform size. Slice the sweet potatoes in similar size for even cooking.
Use dark brown sugar. Dark brown sugar contains more molasses than light brown sugar, providing stronger and deeper flavors of caramel and toffee.
Fresh herbs are best. Although you can certainly substitute dried herbs, fresh herbs are ideal here, delivering the best kind of flavor. This is also a great time to use up all the leftover herbs from your holiday turkey or leg of lamb.
Add finishing touches. Add a little bit of orange zest, fresh herbs or chopped pecans.