Peel the carrots and slice them on the bias (as shown).
In a large bowl, whisk the balsamic vinegar, mustard, garlic powder, thyme, and salt. Slowly whisk in the olive oil. Add the carrots and stir to evenly coat.
Line a baking sheet with parchment paper. Add the carrots in an even layer. Add lemon wedges and fresh thyme to the tray, on top of the carrots.
Roast for 20 minutes. Stir and roast 15 to 20 minutes more (for 35 to 40 minutes total), depending on the thickness of the carrots. Taste and add a few more pinches salt and some fresh ground pepper. Serve.