If you are going to do the Breck to Copper bike path, you might as weel go to the summit of Vail Pass. A little steeper and less oxygen. If that doesn't waste you, just keep on going down to Vail.
Another might be the Saint Marys road out of Idaho Springs, CO. Starts around 8000 ft and tops out somewhere around 14000 ft. I don't know the mileage nor how much is paved.