Remove papery outer skin from garlic (do not peel or separate cloves). Cut top off garlic bulb. Place cut side up in a greased 15x10x1-in. baking pan. Add potatoes; drizzle with broth. Bake, uncovered, at 400° for 30-40 minutes or until garlic is softened.
Remove garlic; set aside. Add the green peppers, green beans and onions to the pan. Bake 30-35 minutes longer or until tender. Cool for 10-15 minutes.
Squeeze softened garlic into a large bowl. Stir in the vinegar, oil, sugar, salt and rosemary. Add vegetables; toss to coat. Serve warm or cold.