It is probably just me, but..

[Shizato]

priority for roulette is - if alot of players are specifically queuing for one particular dungeon, that's where you get placed alot if needed - if you are not needed in a specifically queued dungeon, then its completely random placement from any of the low dungeons based on who in the queue at the time is eligible - IE: if only lvl 30s are next in the queue, you get placed in any lvl30 or below dungeon IF they need you - if everyone next in the queue is max level, its supposed to be a random placement for you all in ANY low lvl dungeon.