Do road bikes use the same width headsets? I know that most commonly MTB's use 1 1/8" steerers and older non-suspension bikes use 1" but I don't really know anything about the width of modern road bikes.  Do they now use 1 1/8" or do they use a different width?
Most modern bicycles, be they road or mountain, use 1 1/8" threadless headsets.  You will occasionally find bicycles, particularly in the lower cost ranges, that will still use an old 1" threaded headset and a threaded quill stem, but these are becoming more and more rare every year.