Preheat the oven to 400°F. Wrap the garlic in tin foil, drizzle with olive oil, and roast until very tender and fragrant, about 20 minutes.
Toss the potatoes on a baking sheet with 2 tablespoons olive oil, rosemary, and a pinch of salt. Roast for 16-18 minutes, until fork-tender
Toss the roasted potatoes with the roasted garlic on the sheet pan, transfer to a serving dish and sprinkle with maldon salt to serve.