You're getting put into those dungeons because other people are queueing up for them, and their group was at the top of the matching list when your turn came up to be slotted into a group. The reason people are doing those dungeons is sort of irrelevant; people are trying to queue for them, and the roulette system is helping fill those groups up. Allowing you to "opt-out" of a certain dungeon or influence what you get matched into in any way goes against the whole reason that it exists. (For example, Stone Vigil would probably get pretty heinous queue times, because a huge number of people would opt out of it for their low-level roulette.)