Preheat oven to 400°F and line a large baking sheet with parchment paper.
Toss the cubed Japanese yam with half of the olive oil and a pinch of sea salt on the baking sheet.
Roast the yams for 15 minutes until they begin to soften.
While yams roast, trim any excess fat from the lamb loin chops and season with chopped rosemary, minced garlic, sea salt, and black pepper.
Remove the tray from the oven, push yams to one side, and add the lamb chops and trimmed asparagus.
Drizzle the remaining olive oil over the asparagus and return the tray to the oven.
Roast for an additional 10 to 12 minutes, or until the lamb reaches your preferred level of doneness.
In a small bowl, whisk together the Greek yogurt, chopped mint, and lemon juice to create a bright sauce.
Serve the roasted lamb alongside the caramelized yams and asparagus, finished with a dollop of the mint yogurt sauce.