Preheat the oven to 425°F and line a baking sheet with parchment paper.

Place the potatoes on the baking sheet and toss with the olive oil, rosemary, salt, garlic powder, onion powder, and several grinds of pepper. Arrange the potatoes in a single layer on the baking sheet, placing them cut side down.

Roast for 35 to 45 minutes, or until the potatoes are tender and browned underneath.

Remove from the oven and toss with the lemon juice. Season to taste with salt and pepper, garnish with parsley, and serve.