Now that I think about it, going back to the part where Thanatos lists who dies, I remember noticing that Dean hadn't been listed as well, but didn't think much of it for some reason.
Back to everything else, you do make a valid point. I can also kind of see Dean abandoning the group when sh*t hits the fan.
Personally, I just hope everyone makes it out okay, and when it happens, I hope Roswell will pass away knowing his friends are alive and safe.