Place top oven rack in the center position and pre-heat oven to 400°F.Line a large, rimmed baking sheet with parchment paper or a Silpat® baking mat and set aside.
Whisk one tablespoon olive oil with the orange zest, orange juice,honey, and mustard. Season with salt and black pepper, to taste,and stir to combine.
Rub the orange glaze all over the pork loin, making sure to coat it on all sides. Place the meat in the center of the prepared sheet pan and set aside.
Toss the beets, carrots, and red onion with the remaining olive oil and thyme leaves. Season with salt and black pepper, to taste, and spread the seasoned veggies around the pork tenderloin in a uniform layer without overcrowding.
Place the sheet pan in the pre-heated oven and roast for 25-30 minutes, or until the pork reaches an internal temperature just above 140°F* and the veggies are fork tender.
*Note: 145°F is the recommended minimum safe cooking temperature for pork tenderloin -the internal temperature will rise several degrees while it rests. The meat may be a little pink at this temperature.
Remove from oven and loosely cover the roast with aluminum foil. Allow the meat to rest for 5-10 minutes before serving. Enjoy!