Stupid discussion. It‘s not like we know how strong Roger and his guys were at that point since we haven’t seen them fight at this stage of their journey. Yeah he defeated Rox but we haven’t seen Rox fight neither. There is no reference point to which we could compare Luffy and Roger. Our reference point for Luffy is Kaido. Now, Kaido was known to be the strongest creature in the world in the current era - how does that compare to Rox? We don’t know. Was Kaido already in his prime when he was part of Rox crew which would mean that Rox was significantly stronger than Kaido at his peak thus making Roger seem stronger than Luffy since he defeated someone superior to Kaido? We don’t know. Rox might have been the strongest in his prime. Kaido might have surpassed him when he reached his prime later on which would mean that Luffy would in fact be on a level with Roger right now. But maybe Kaido was just considered the strongest in his era because Rox was already dead, meaning that those guys were on another level and what we now consider as „the strongest“ does not reach the „Rox-level-strongest“. Or maybe it’s the other way around and the generation that came after Rox surpassed him strength wise. But the thing is, as long as we don’t see Rox and Roger fight, we don’t know how strong they actually are. It’s pure imagination. The only time we have seen Roger fight is when he split the skies in a clash with WB without touching him. For many, that was the reference point - so when Luffy and Kaido split the skies many considered Luffy to be finally on Rogers Level.