Preheat the oven to 425°F. Arrange the cubed butternut squash and halved Brussels sprouts on a rimmed baking sheet.
Pour 1½ tablespoons of olive oil over the squash and Brussels sprouts. Add salt and black pepper to taste, then toss thoroughly by hand until every piece is evenly coated.
Spread the seasoned vegetables across the baking sheet in one uniform layer to encourage consistent browning.
Place the baking sheet in the heated oven and roast the vegetables for 10 minutes.
Remove the pan from the oven and toss the vegetables so that additional surfaces can brown. Rotate the baking sheet, moving the front edge toward the back of the oven.
Return the vegetables to the oven and roast for another 10 minutes, or until they are tender and visibly caramelized around the edges.
While the vegetables are roasting, place the unsweetened apple cider, apple cider vinegar, and minced onion in a small saucepan.
Bring the liquid to a boil over medium heat. Lower the heat and simmer for approximately 8 minutes, or until the volume has reduced by half.
Remove the saucepan from the heat and carefully transfer the reduced cider mixture to a jar. Add the Dijon mustard, maple syrup, 1 tablespoon of olive oil, salt, and black pepper.
Secure the lid tightly and shake the jar vigorously until the dressing is fully blended.
Transfer the roasted butternut squash and Brussels sprouts to a serving bowl or platter. Scatter the dried cranberries and toasted chopped pecans over the vegetables.
Spoon a portion of the apple cider vinaigrette over the salad and toss gently. Taste and add more vinaigrette, salt, or black pepper as required before serving.