Another Alps route that you can do in your road bike, is the Chamonix - Mont Blanc / Col de la Forclaz. The same as the Chamonix - Mont Blanc / Col de Montets route, you will find every summer day cyclists doing this famous tour in a road bike.
Is not a very long ride, but you will cross the border to Switzerland! The return to Chamonix is beautiful, especially the top of the Col des Montets, with a superb view of Mont Blanc.
The itinerary (from France to Switzerland): Chamonix - Mont Blanc / Argentière / Col des Montets / Chatelard (border with Switzerland) / Col de la Forclaz / return to Chamonix - Mont Blanc.
Numbers: 50km and 1145m D