Who wrote the passage on the Poneglyph at Skypiea? In chapter 507 the Straw Hat crew meets Rayleigh for the first time. It was then that Robin asked whether Roger was able to understand the ancient language used on the poneglyphs, because at Skypiea she had come across a poneglyph with a passage written on it, supposedly signed by Roger. Yet Rayleigh said that they were merely pirates and that Roger could not match the intellect of those of Ohara. So then in the end, who did write the passage?


  I have come here, and will lead this passage to the very end. - Pirate Gol D. Roger
It seems that we finally know. Oda revealed in chapter 818 that...


  ...it was most likely Lord Kouzuki Oden that wrote down that passage. The Poneglyph were created by the Kouzuki clan and it was confirmed that Lord Oden was able to read the language and write on the stones.

 

 Later it was revealed that he himself had travelled with the former Pirate King, Roger. So chances are that he travelled along with Roger to Skypiea and wrote that additional paragraph.