Preheat your oven to 400°F and line a large sheet pan with parchment paper to ensure the vegetables roast perfectly without sticking.
Peel the sweet potato, carrots, and parsnips, then dice them into uniform 1-inch pieces so they cook at the same rate as the pork.
In a bowl, toss the root vegetables with 0.75 tablespoons of olive oil, half of the rosemary, half of the thyme, and a pinch of salt and pepper.
Pat the pork tenderloin completely dry with a paper towel, then rub it with the remaining 0.75 tablespoons of olive oil, garlic powder, and the rest of the herbs.
Arrange the seasoned vegetables around the edges of the sheet pan, leaving the center open for the pork tenderloin to sit directly on the pan.
Roast for 20 to 25 minutes, or until a meat thermometer inserted into the thickest part of the pork reads 145°F for a juicy, tender result.
Transfer the pork to a clean cutting board and let it rest for at least 5 minutes before slicing into 1-inch thick medallions.
Serve the pork medallions alongside the golden roasted root vegetables, finishing with any remaining herb-infused oil from the pan.