The sad thing about mentor roulette is you have to be prepared to set aside 60-90 minutes of your time to 1 roulette due to extreme trials being in there. It only gets worse because extreme trials like Shinryu is in there now which pretty much makes it a 60 minute learning party with a very small chance to clear and worse part no rewards at the end for even trying as a mentor.

The best thing you can get in mentor roulette is a guildheist.