Preheat your oven to 425°F. Line a baking sheet with parchment paper.
In a bowl, combine the lean ground beef, egg, breadcrumbs, garlic powder, salt, and pepper. Mix gently until just combined, being careful not to overwork the mixture.
Form the mixture into small meatballs, approximately 1 to 1.5 inches in diameter, and set aside on a plate.
Cut the potato into small cubes. Toss them in olive oil, rosemary, salt, and pepper until evenly coated.
Spread the potato cubes onto the prepared baking sheet. Roast in the preheated oven for about 20-25 minutes, or until the potatoes are golden and crispy, stirring halfway through.
While the potatoes are roasting, heat a non-stick skillet over medium heat. Add the meatballs and cook, turning occasionally, until they are browned on all sides and cooked through, about 10-12 minutes.
Steam the broccoli in a steamer basket over boiling water for about 4-5 minutes until tender yet crisp.
Divide the meatballs, roasted potatoes, and steamed broccoli among plates. Serve immediately and enjoy your balanced, flavorful meal.