We know 0.2% of his actual journey.
- Sengoku, the fleet admiral who hates pirates, goes out of his way to address Roger with his proper title "King of the Pirates", multiple times.
- Sakazuki, the fleet admiral who hates pirates, holds reverence for Roger as the Pirate King, somebody who sat on the throne as the peak.
- Garp, same way holds Roger in extremely high regards and the only one who he thought was worth competing with out of their generation of pirates.
- Narrator, in this very flashback addresses Roger with respect making sure to highlight Roger being King of the Pirates before while listing down Rocks pirates their hype.
To call Roger a fraud is to essentially call all these characters frauds, even though they've seen Roger's journey.