In a medium bowl, toss sweet potatoes with olive oil, balsamic vinegar, salt and pepper, raisins and shallots.
Place sweet potato mixture in a 9x13 inch-baking dish.
In a skillet over medium heat, melt butter. Add pecans and stir until fragrant, about 3 minutes. Add maple syrup and stir until most of the liquid has been absorbed, about 3 minutes.
Top potatoes with caramelized toasted pecans, cover with aluminum foil and bake in preheated oven 50-60 minutes or until sweet potatoes are tender.