Preheat the oven to 400 degrees F. Mince the garlic really finely, then strip the leaves off the rosemary sprigs and mince them finely, too.
Melt the butter in a small skillet over medium heat, then throw in the rosemary and garlic. Reduce the heat to low and simmer 10 minutes, or until the butter is totally infused.
Arrange all of the potatoes on baking sheets and toss with the butter mixture. Roast 35 to 45 minutes, or until the potatoes are tender and nice and golden brown. Arrange them on a large platter, add salt and pepper to taste and sprinkle the parsley over the top.