Preheat oven to 400°F (204°C).
In a large mixing bowl, toss the potato pieces with olive oil, rosemary, garlic, salt, and pepper until evenly coated.
Spread the potatoes in a single layer on a large rimmed baking sheet.
Roast for 45 minutes, turning the potatoes with a spatula every 15 minutes to ensure even browning.
Remove from oven when golden brown and tender, then serve immediately.