No, the roulettes are definitely a bug (or an unfortunate side effect of priority changes) as many people have reported:

If you queue Expert Roulette as a healer you'll likely get huge queue times (if it ever pops). However, if you queue healer for both the dungeons manually, you'll get the usual fast queues. This is pretty consistent.

My speculation is that they've given manual queuing priority over roulette. This kind of makes sense for many dungeons as it allows those that want a particular dungeon to get it. However, for Expert Roulette it for instance means that if tanks are queuing at the same rate as healers queuing manually, then healers on roulette will never get in, as there is always a healer queueing manually ahead of them in the queue.