Place the cubed sweet potatoes in a large mixing bowl. Add the olive oil, smoked paprika, garlic powder, ¼ teaspoon salt, and ⅛ teaspoon black pepper. Toss to coat evenly.

Spread the sweet potatoes in a single layer on the prepared baking sheet.

Roast for 25 to 30 minutes, flipping halfway through, until tender and lightly browned.

While the sweet potatoes roast, melt 1 tablespoon butter in a large skillet over medium heat.

Add the sliced onion and cook for 5 minutes, stirring occasionally.

Add the mushrooms and cook for 6 to 8 minutes, until softened and lightly browned.

Stir in the minced garlic and dried thyme. Cook for 30 seconds, stirring constantly.

Transfer the onion and mushroom mixture to a plate.

Reduce the heat to medium-low and melt the remaining 2 tablespoons butter in the skillet.

Add the Worcestershire sauce and beef broth. Stir until blended with the melted butter.

Add the leftover prime rib, remaining ¼ teaspoon salt, and remaining ⅛ teaspoon black pepper. Toss gently to coat with the sauce.

Cook for 2 to 3 minutes, stirring occasionally, until the prime rib is heated through. Avoid cooking longer than necessary to keep the beef tender.

Return the onions and mushrooms to the skillet. Stir gently to mix with the beef and sauce.

Divide the roasted sweet potatoes evenly among 4 serving bowls.

Spoon the prime rib, onions, and mushrooms over the sweet potatoes. Drizzle with the remaining garlic butter sauce.

Sprinkle with chopped fresh parsley and serve.