Sengoku states that garp was the one who took down the rocks pirates.
The reason this was hidden was because he had to work with pirates, specifically the Roger pirates.
Not only that but he also did it to defend celestial dragons, and know we know that the Holy knights were present which means that this battle was the entirety of the rocks pirates vs Roger pirates + garp and his marines + holy knights.
We also see an illustration of garp and roger standing side by side against rocks which further leads me to believe that they worked together to beat him, that alongside the statement that
they joined forces to beat the rocks pirates. Furthermore, Rocks was betrayed at God valley, and that was his downfall despite having a nigh-unbeatable crew, this diminishes the possibility that Rocks had help in the fight.
Of course, we don't know what actually happened, that's why I said that until we get actual feats and confirmation of what happened, we can only go off of these implications.
All in all, this points to Rocks being decently above the cast of characters at that time.
He is also outright stated by sengoku to be Rogers greatest foe, and in another translation (anime), his strongest foe.
As always, your display of limited reading comprehension is palpable. I have clarified everything above, please have a read before saying I'm trolling or biased.
Edit: I left scans all over the post but they were deleted for some reason. I'm quoting everything from chapter 957 on tcb scans. If you need citation for anything, please inform me.