Preheat the oven to 425°F. Lightly grease a large baking sheet and set it aside.
In a medium bowl, whisk together the olive oil, Dijon mustard, maple syrup, dried mustard, garlic, and thyme.
In a large bowl, combine the sausage, broccoli, Brussels sprouts, sweet potatoes, and red onion. Pour the glaze over the mixture and toss until evenly coated.
Spread everything evenly on the prepared baking sheet.
Roast for 25–30 minutes, stirring halfway through, until the potatoes are fork-tender and the vegetables caramelize.
Serve warm and enjoy!
Notes
Store: Refrigerate leftovers in an airtight container for up to 4 days.
Reheat: Warm in a 350°F oven for 10–15 minutes or reheat in a skillet on the stovetop until hot.
Freeze: Spread cooled leftovers on a baking sheet to flash-freeze, then store in freezer bags for up to 2 months. Reheat directly from frozen.
Make ahead: Chop veggies and sausage up to 24 hours in advance, then toss with glaze and roast when ready.