What did Jinbe lose in Charlotte's roulette?
As stated in chapter 834 afterward, Jinbe didn't go through with the roulette because it is set up in a way that somebody who does it will probably lose his life and that wasn't what he wanted because of his pledge to Luffy.

So he just went for the normal thing somebody would do and he betrayed her in chapter 851 by freeing Luffy from the prison and escaping together with them from Big Mom.