In a large bowl toss the brussels sprouts and butternut squash in the oil and spread over one of the sheet pans. Roast for 45 min or until the squash is tender. Stir every 15-20 minutes to evenly cook all sides.
While the vegetables are roasting toss the pork belly or bacon in a bowl with a tablespoon of the vinegar and a tablespoon of the maple syrup to coat. Pour on the second lined sheet pan and set aside. After the vegetables have been roasting for 30 minutes place in the oven and removed when cooked. Depending on the thickness of the protein this could be less than the remaining 15 minutes.
In a saucepan heat the remaining maple syrup and balsamic vinegar until it boils and stir until the mixture thickens to a syrup.
When the vegetables are done toss them, the pork, and maple-balsamic reduction together to coat evenly.