1. Preheat the oven to 350°F. In a medium bowl, toss the pecans in the salt, vanilla extract, maple syrup, cinnamon, and melted butter. Spread the mixture evenly over a parchment-lined baking sheet. Toast in the oven for 5-10 minutes until sticky and caramelized. Watch to ensure they do not burn. Remove the candied pecans from the oven and set aside.
2. Increase the oven temperature to 400°F. In a large bowl, toss the cubed sweet potatoes in the olive oil, salt, maple syrup, brown sugar, and cayenne pepper until evenly coated. Spread the potatoes on a baking sheet and roast for 35-40 minutes until the sweet potatoes are tender. Turn the sweet potatoes halfway through to ensure even roasting.
3. Use a wooden spoon to gently fold the pecans into the potatoes. Return the mixture to the oven and roast for another 5-8 minutes until the potatoes begin to brown at the edges and the pecans are toasty.
Remove the baking sheet from the oven. Sprinkle with salt and pepper to taste and serve warm.