The pre 50 roulettes are meant to be played solo and the bonus is exactly for that. It is fine, as it is.

Before anyone decides to chime in, Yes, I know you can flag individual content that would fall into those categories, but lets face it, queue times can be a total pain and some do enjoy the surprise (or groan) factor of a random selection.
You can mark ~5 or 6 dungeons. Do it, and you will have your "random selection".