Nothing more than a Crazy Old Man.... probably.
The Party has acquired the following information about Roshi and his Gym Challenge
Roshi’s Gym Challene is a standard, 1v1 fight in a heavily reinforced boxing ring. Trainers who attempt to beat the gym with fliers quickly learn that his pokemon are adept at using the ropes as a springboard to engage those who would fight from beyond melee range.
His Challenge roster consists of Fighting Types from level 15 – 20
Once Defeated, Roshi gives Trainers the Ki Badge, A sky blue starburst with a fist inside of a circle, both outlined in silver. The Ki Badge grants Trainers the 1 time choice of giving all of their pokemon the Inner Focus Ability, or to set their Default Combat Stage in attack to +1
Trainers also gain a TM for Bulk Up, and 10,000 Poken.
Roshi does not hand out Custom Move HMs or the like to anybody on their first gym challenge, hence why he encourages Trainers to come back and fight him again some day.
Roshi’s Gym also offers retraining/training services for any Martial Artist stuff, and will teach Bulk Up and Focus Energy go any trainer who spends a week at the gym attempting to learn the move.
Summoned by the ringside bell in Pewter City’s Gym, this old man favors comfy shorts, seaside shirts, carries an old gnarled staff, and is characterized by his gap toothed grin, scratchy voice, and sideways comments towards women.
For whatever reason, This decrepit geezer has been placed in charge of handling any challenging trainers.
maybe they just sic him on the new trainers, and keep the real Gym Leader hidden away for proper fights.