For the roasted vegetables: Preheat the oven to 400 degrees F.
In a large bowl, toss the onions, sweet potatoes, Brussels sprouts, butternut squash, carrots, fingerling potatoes and garlic with the oil, salt and pepper on a large jelly roll pan. Spread the vegetables in an even layer and roast, stirring once halfway through, until tender, 40 to 45 minutes. Remove the garlic from the skins before serving.
For the glaze: Meanwhile, in a small saucepan, combine the vegetable broth, oil, vinegar, honey, mustard, lemon juice and some salt and pepper. Cook over low heat until the glaze is reduced by half, about 10 minutes. Serve over the vegetables or as a dipping sauce.
Country Dijon is a milder, creamier version of Dijon mustard. If country Dijon is not available, mix 1 teaspoon regular Dijon with 1 teaspoon mayonnaise.