1. Preheat oven to 450°.
2. Remove white papery skin from garlic head; separate but do not peel cloves. Place garlic, olive oil, potatoes, thyme sprigs, and rosemary sprigs in a large bowl; toss to coat. Arrange potato mixture on a foil-lined jelly-roll pan. Sprinkle evenly with 1/4 teaspoon kosher salt and pepper. Bake at 450° for 25 minutes, stirring after 13 minutes. Sprinkle with 1/8 teaspoon kosher salt and parsley.