User blog comment:Neowitch/700 - Breakfast at Mugiwara's/@comment-1454981-20130227135301/@comment-3425840-20130227224409

Well Shiki was NOT the top tier, not after he got beaten y pre time skip Luffy no matter how much plot armor involved.

Garp was Roger's rival to a greater extent that Shiki was and Garp does not have a df (at least not known yet).

Rayleigh does not have a df - confirmed and he is crazy strong - admiral level, implying he could give WB a run for his money.Yes he would ultimately lose but it would have been a tough fight.

Shanks does not have a devil fruit (yes he might have eaten one but there has been no sign made that he actually did) - he is an Yonko and also dared to approach an angry Whitebeard or stop Sakazuki (never used any df ability what so ever).

Mihawk is the greatest swordsman in the world, he does not have a df (at least not known to have).

All these high level figures could reach this high without df so there is no reason Roger could not. In fact if he did have a df then it would imho reduce his grandeur.

I am not saying he did not have one, he might have had one. What I am saying is that just because he was the strongest there is no guarantee that his strength was df based.