The numbers tell one side of the story, but then there's the "fight" for wins, the skill on display & the names of the rivals which also plays a huge role in the legacy of a sportsman. It all comes down to raw talent & how public perception defines who's best irrespective of the numbers.
Take Ayrton Senna for example: his numbers aren't the best (he has 3 F1 world titles), but in conversations about the formula 1 "goat" his name is pretty much at the top of the list. That's because he's viewed as the best driver of all time. He might not have won the world title all the time but the drivers he fought against (Lauda, Prost, Mansell, Piquet, Schumacher etc.) created that idea he was the greatest even when he didn't win.
Now that was an extreme example, but the same rules apply to a certain extent with Roglic, i.e. it's not just about the wins & numbers he has already achieved & can still achieve in the coming years, it'll also be about the memorable performances & fights. Rides like his win at the Lagos de Covadonga or his battle against Pogacar in Basque Country mean more (at least to me) than Nibali (for example) thrashing Jean-Christophe Péraud in the 2014 Tour or Froome crushing Romain Bardet.
The same applies to riders like Wout van Aert & Mathieu van der Poel as well, i.e. their victories mean more based on "who" they're beating (each other, namely) & their defeats also mean less because the public knows the guy who won is a top top talent. Like at the Tour of Flanders last year there was no one pointing their finger at WVA & shouting "what a loser!". No, because MvdP is a legend.