How would you neatly and consistently round over the ends of dozens of 1/2" dowels?

How long are the dowels? They don't appear to be too long, even if they are 24" it should be manageable. Mount a belt sander mounted upside down, either secured in a vise or a bar clamp to a table. Hold the dowel with a drill with a 1/2" chuck and go to town. You may also want to use something as a tool rest to steady the working end of the dowel close to the sander. Rough shape the dowels first then go back and finish the ends using the same technique, only this time clamp the drill down and hand hold the sandpaper, steel wool, scotch brite, etc.