Preheat oven to 400°F and line a large rimmed baking sheet with parchment paper for easy cleanup.
In a small bowl, whisk together the maple syrup, Dijon mustard, garlic powder, and finely chopped rosemary.
Place the halved Brussels sprouts and cubed sweet potatoes on the baking sheet, tossing them with olive oil, sea salt, and black pepper.
Season the pork tenderloin with a pinch of salt and pepper, then sear in a hot skillet for 2 minutes per side until a golden crust forms.
Move the pork to the baking sheet and brush half of the maple-Dijon mixture over the top and sides of the meat.
Roast for 18-20 minutes, brushing the remaining glaze onto the pork halfway through, until the meat reaches an internal temperature of 145°F.
Remove from the oven and let the pork rest for 5-10 minutes before slicing into thick, juicy medallions.