Preheat oven to 425°F. Pat thighs dry, season with salt and pepper.
Toss carrots with 1 tbsp olive oil, salt, and pepper; spread on a rimmed baking sheet.
Sear thighs skin-side down in a hot skillet with 1 tbsp oil until golden, about 6–8 minutes; flip briefly.
Whisk maple syrup, soy sauce, vinegar, garlic, and ginger in a bowl.
Transfer thighs to baking sheet with carrots, brush half the glaze over thighs and carrots.
Roast 20–25 minutes until thighs reach 165°F and carrots are tender, brushing with remaining glaze once more.
Rest 5 minutes, garnish with parsley and toss carrots with butter if desired.