Just like Luffy is stupid and can't understand Poneglyphs, Roger would've have been no good but he might have had a nakama like Robin, probably from Ohara, who may not only be able to read Poneglyphs but also might have a mastery in Poneglyph writing. Seeing Rayleigh mentioning about the Ohara tragedy, makes me think that that Nakama from Ohara was probably separated from others after Roger and with the end of Ohara, Rayleigh would've realised that he even lost another Nakama or maybe Rayleigh just have known the background of Robin (I can't declare for sure). That thing about Rayleigh saying "ability to hear" things is too inexplainary and not adequate to jump to any sort of conclusions but I gues Oda is probably preparing for a new ability for future like he did with Haki. That thing about Ability to Hear is similar to what Zoro had experienced during the Alabasta Arc while fighting Mr. 1. He was able to feel/hear the steel, rock, leaves, etc. But I still can't relate it to this Rayleigh's proposed Hearing Abiltiy theory. So I guess it would've been the work of a scholarly Roger Nakama like Robin.