Preheat oven to 400 degrees. In a large bowl, toss new potatoes and garlic cloves with rosemary. Toss with olive oil to coat lightly and add salt and pepper to taste. Lightly oil a sheetpan and spread potatoes out into one layer, cut side down. Roast for 30 to 45 minutes or until golden brown and tender. Remove from oven and let cool for 20 minutes before removing with a spatula. Serve hot or cold.