Preheat the oven to 400°F (200°C). Line a large baking sheet with parchment paper or foil for easy cleanup.
In a medium bowl, combine the pure maple syrup, Dijon mustard, olive oil, paprika, dried parsley, kosher salt, and ground black pepper. Stir until smooth and fully combined.
Dip each chicken thigh into the maple Dijon glaze, coating all sides evenly. Arrange the chicken thighs on the prepared baking sheet.
In a large bowl, combine the sweet potatoes, Brussels sprouts, red onion, and bacon. Pour the remaining maple Dijon glaze over the vegetables and bacon, then toss until evenly coated.
Spread the coated vegetables and bacon around the chicken thighs in an even layer on the baking sheet.
Roast for 45–50 minutes, or until the chicken reaches an internal temperature of 165°F and the vegetables are tender and lightly caramelized.
Let cool slightly before serving.