Preheat your oven to 425°F and line a large sheet pan with parchment paper for easy cleanup. Position the oven rack in the upper-middle position so your vegetables and sausages roast quickly and evenly.
In a small bowl, whisk together olive oil, garlic powder, paprika, dried thyme, dried rosemary, salt, black pepper, balsamic vinegar, and Dijon mustard. This aromatic mixture will coat all your ingredients and create incredible flavor throughout the chicken sausage dinner.
Place baby potatoes, Brussels sprouts, bell pepper, and red onion in a large bowl, then pour the herb mixture over top. Toss everything together until vegetables are evenly coated, ensuring no dry spots remain in the mixture.
Arrange coated vegetables on your prepared sheet pan in a single layer, creating space in the center for sausage links. Place loaded sheet pan chicken sausage links directly on top, nestling them slightly into the vegetables for even cooking and browning.
Roast everything for 22–25 minutes until sausages reach an internal temperature of 160°F and potatoes are fork-tender. The vegetables should have caramelized edges and the Brussels sprouts should look golden brown and crispy.
Remove the sheet pan from the oven and let rest for 2 minutes before plating. This brief resting period allows juices to redistribute and flavors to settle into the dish.