Preheat oven to 400°. Cut top of garlic head off, about one-quarter of the way down. Drizzle 1 teaspoon oil over exposed cloves; season with a small pinch of salt. Loosely wrap in foil.
Roast garlic until cloves are golden and softened, about 30 minutes. Let cool until cool enough to handle.
In a food processor or blender, blend roasted garlic (without the papery skins), beans, lemon juice, rosemary, and ¼ cup oil until smooth; season with salt, black pepper, and red pepper flakes. Continue to blend until combined, then taste and adjust seasonings.
Transfer dip to a serving bowl. Drizzle with oil. Top with rosemary. Serve with chips alongside.
