Yeah, Roger being equal if not stronger than Whiteboard doesn't make much sense imo. Whiteboard basically had everything that Roger had (top tier haki, highly graded weapon, beastly physical stats) in addition to having the most destructive devil fruit. Roger being stronger because "better haki" is quite boring and uncreative. Same with Garp, he was able to keep up with those two because he punched really hard?
Imo, it'd have been better if Whitebeard just had basic haki and was as strong as he was primarily cause of his devil fruit. While Roger was the one with top tier haki and swordsmanship and kept on par with Whitebeard due to that. Otherwise, it just leaves a gap in logic for how Roger could conceivably be on the same level as Whitebeard when Newgate had everything he had and then some.