Preheat the oven: Preheat your oven to 400°F and line a large sheet pan with parchment paper or foil for easy cleanup.
Cut the sweet potatoes: Peel the sweet potatoes and cut them into even 1-inch cubes so every piece cooks at the same rate.
Mix the glaze: In a large bowl, whisk together the olive oil, melted butter, maple syrup, cinnamon, salt and black pepper.
Toss to coat: Add the sweet potato cubes to the bowl and toss until every piece is coated evenly in the maple mixture.
Spread on the pan: Arrange the coated cubes in a single layer on the prepared sheet pan, leaving space between pieces so they roast rather than steam.
Roast the first batch: Bake for 20 minutes, until the bottoms start to turn golden.
Flip and add pecans: Remove the pan, flip each piece with a spatula, and scatter the chopped pecans evenly over the top.
Finish roasting: Return the pan to the oven and roast for another 10 to 15 minutes, until the edges turn deep amber and slightly sticky and a fork slides in easily.
Rest briefly: Let the pan sit for 5 minutes off the heat so the glaze sets slightly before serving.
Garnish and serve: Sprinkle fresh thyme leaves over the top, if using, and serve warm.
