Make this for our Roasted-Vegetable Salad.
Preheat oven to 400 degrees. Wrap garlic in foil. Roast until very tender, about 1 1/2 hours. Let cool slightly. Can be refrigerated in an airtight container overnight.
Cut the garlic head in half crosswise. Squeeze pulp into a small saucepan, and place over medium-low heat. Whisk in vinegar and rosemary. Gradually add oil, whisking constantly. Use immediately.