Start by scrubbing the potatoes and chopping them into approximately 1 inch (2.5 cm) chunks. Place these in a mixing bowl with some salt and pepper, then add the chopped rosemary, garlic, lemon juice and olive oil. Toss the potatoes around to get them nicely coated with the oil and other ingredients. Arrange the potatoes on a solid, shallow baking tray, in a single layer, then roast on the highest shelf for 30-40 minutes until crisp and golden. Serve straight from the oven.
Pre-heat the oven to gas mark 7, 425 F (220 C).