Chat GPT's take on the matter:
In the context of this dialogue, it's not necessarily saying that Scopper Gaban is exactly equal to Roger in terms of raw strength, but rather that he is a legendary figure of similar stature and significance.
The mention of Scopper Gaban being compared to Gol D. Roger and Silvers Rayleigh suggests that Gaban is an incredibly powerful and respected figure, possibly on a similar level, but we haven't seen direct confirmation of his full abilities compared to Roger.
Gaban's reputation as a "legendary figure" likely means he was a key player in the Pirate King's crew, and his strength could be on par with some of the strongest characters in the world, but the comparison isn't necessarily implying he's at the exact same level as Roger in every aspect (for instance, Roger was known for his leadership and being the Pirate King).
It is intriguing though, as Scopper Gaban is now shown as being ready to face Luffy, which could mean he's an extremely competent fighter and will likely put up a strong challenge.