Sometimes the low level roulette does put you into a 51-59 dungeon, even though those numbers are bigger than the 50 of high level roulette. Maybe the names could be changed a bit. When it sends you into a sub-50 one that's usually to benefit new players. I've had the same thing as you where I once got into AV randomly and everybody was lv synced down to it. I figured we were all roulette people and just skipped as many mobs as we could sneak past.