Shiki has the most active role so far in Rocks which is suprising, i thought it would be WB
Rocks was all about ambition and schemes.
Everything we know about Shiki, canon and non-canon, indicates Shiki was the most like Rocks, out of the Rocks Pirates we've seen up close, in terms of recruiting, scheming, and ambition.
If the Galley-Ra Shipwrights were involved in Pluton's creation, then it looks like Rocks was after Pluton, like Shiki most likely was, too (Shiki canonically wanted Roger to join him to take an Ancient Weapon. Doubt it would be Uranus, that's Imu's, and no way it was Poseidon based on the timeline).
Chapter 0 IS canon. Shiki did fight Roger after asking him to join forces to get an Ancient Weapon.
This leads me to always wonder: is the end of Chapter 0 canon, then? What if Shiki's 20 year plan is real: we just haven't seen it yet? What if his canon plan is completely different from his non-canon plan?
IMO Oda is using this flashback to set up some of the surviving Rocks Pirates, as well (not including Kaido and Linlin who are also still alive)