Heat the oven to 400°F. Grease a 12-cup muffin tin. In a large bowl, combine the ground beef, egg, breadcrumbs, milk, onion, Worcestershire sauce, garlic powder, salt, and black pepper. Mix gently until just combined.
Cut each bacon slice in half crosswise. Press one half-slice around the inside edge of each of eight muffin cups, with the ends slightly overlapping. Divide the beef mixture among those cups and press it in lightly.
Stir the ketchup and brown sugar together in a small bowl. Spoon the glaze over the meatloaf muffins, spreading it across the tops.
Toss the halved potatoes with the olive oil and dried rosemary. Spread them in a single layer on a rimmed baking sheet, cut sides down. Place the muffin tin on the same oven rack, if space allows, and bake both for 25 to 30 minutes. The potatoes should be tender and browned, and the beef should reach 160°F in the center.
Let the muffins rest for 5 minutes before removing them from the tin. Serve with the roasted potatoes.