I'm not sure exactly what to think. This is either the most naive or the most troll request I've seen in the forums for a while. If it's troll and you just wanted to bait people into responding, well done, because you got 4 pages worth of responses.

I'm going under the assumption that it's naive, and I would like to reiterate what most other posters have said and also further elaborate on some points.

The Adventurer in Need bonus is there to encourage people to play a certain class that is needed to ease up the queues of that particular roulette. I see no reason to advocate for a "you're using roulette as X class have some bonus too" type AiN. At best, it would be such a small bonus (since the AiN bonuses are highly negligible anyway and it would have to be less than the primary AiN bonus) that it wouldn't make a difference to the bigger picture (akin to asking for an extra 1 xp from every mob or so, sure it helps, but it begs the question as to why such an infinitesimal gain should be prioritized for implementation). At worst, if the bonus is substantial and is given to classes which are not in need, this would make the queue times even more bloated than they are currently for those classes.

There's a reason why Tanks are there non-stop. Its cos tanks are always needed.

You want the bonus? Like Nadirah said above, you play the class in need. You're not in need? No bonus. Sorry.