A picture of it happening:
http://i.imgur.com/hw1TCKG.jpg
As you can see, it doesn't even show me as being queued in the Duty Status window. Just 0 people in all the way around. So far I've only seen it happen with Expert Roulette and Level 50 Dungeons Roulette. Edit: Make that Level 60 Dungeon Roulette too.