Second this. I believe this was it in their prime, obviously during different times they met one could have the advantage but when it was all said and done:
SS-tier
Rocks
S-tier
Roger -> WB -> Garp
A-tier
Rayleigh -> Shiki -> Oden
Roger ≈ WB ≈ Garp in a normal setting but when the situation calls for it Roger had an extra gear just like Luffy. When up against Lucci or Katakuri he somehow pulled off the victory even though they were both stronger than him just because he knew everyone would be slaughtered otherwise. I can't remember who said it about Roger (Garp?) that he would turn into a demon if his crew was in peril, this to me means he was around WB/Garp-level normally and seeing as they are good guys he never turned into a demon against them thus they fought rather equally. But up against Rocks he had to kick into overdrive, a level WB and Garp lacked. Something unique to Roger and Luffy. If he had lived maybe also Ace and perhaps Sabo as well.
And just like Shiki, a swordsman with an OP-fruit from the looks of it was probably above Rayleigh at first, ultimately Rayleigh became WSS. Just like Zoro vs Law.