Heat the oven. Set the oven to 425°F and line a large rimmed sheet pan with parchment.
Cut the squash. Trim both ends, halve the squash lengthwise, scoop out the seeds, and slice each half crosswise into 1/2-inch half-moons. Leave the skin on.
Coat the squash. Toss the half-moons in a large bowl with the olive oil, maple syrup, salt, and pepper until every piece is glossy.
Arrange in one layer. Spread the squash on the pan in a single layer with space between pieces, so the edges roast instead of steaming.
Roast. Roast for 25 minutes, flipping the pieces once halfway, until tender with deeply golden edges.
Toast the pecans. Scatter the pecans over the pan for the last 7 minutes of roasting, until fragrant.
Serve. Slide the squash onto a warm platter, spoon any pan glaze over the top, and serve warm.