Prime Roger had at least 2 equals, Garp and WB, Someone like Sengoku could prob push him to high-extreme dif
It only makes sense for there to be at least one character as strong as Roger today, by their side by side portrayal that's Dragon if not more, closely followed by Shanks, Kaido, Akainu, Mihawk ...
Oda isn't an idiot he won't make Roger a god noone can touch, to make the story work you need chatacters that can push him very, very far
Roger, Garp and WB aren't less than high difing an Admiral