Preheat your oven to 425°F (220°C). Line a large sheet pan with parchment for easy cleanup.
Prepare the vegetables: Peel and cube the sweet potatoes into roughly 1-inch pieces. Slice the red onion into wedges.
In a small bowl, whisk together honey, Dijon mustard, apple cider vinegar, minced garlic, olive oil, thyme, paprika, salt, and pepper to make the glaze.
Pat the chicken thighs dry with paper towels and season them lightly with salt and pepper.
Arrange the chicken thighs on the sheet pan, skin side up. Scatter the sweet potato pieces and onion wedges around the chicken.
Pour about two-thirds of the glaze over the chicken, turning the pieces to coat. Spoon or drizzle the remaining glaze over the vegetables as well.
Roast in the oven for 30–35 minutes, until the chicken reaches an internal temperature of 165°F (74°C) and the potatoes are tender. If the chicken skin isn’t as crispy as you’d like, broil for an additional 1–2 minutes, watching closely.
Remove from the oven and let rest for 5 minutes before serving to allow the juices to redistribute.