Just before Roger was executed, he announced to the globe that this wonderful treasure might be claimed by anybody who could reach it, therefore starting The good Age of Pirates.
Theres a little discussion in regards to the greatest time to slide Z casino into your timeline. Its viewers alternative: cue it up soon after episode 573 or wait around till the top with the Zs Ambition arc with episode 578. Whichever you choose, not viewing it would be a slip-up.