Heat the oven to 400 degrees F. In a bowl, toss the squash with the olive oil, salt, pepper and rosemary.
Transfer to a baking sheet* and roast until soft (about 35 minutes). Stir everything around half-way through the roasting time.
Melt the butter in a saucepan. Add the pecans and stir them around on medium-high heat for a minute. Add the sugar and stir around on medium heat until the sugar is melted and the pecans are evenly coated (a few minutes).
Toss the pecans with the squash and serve.
*I recommend using a dark metal sheet pan to brown the squash nicely from the bottom.
Rosemary Butternut Squash with Brown Sugar Pecans https://thespicetrain.com/rosemary-roasted-butternut-squash/