Plot shields for a protagonist are a trope most manga protagonists have, the manga would be a lot more dull if Luffy didnt find himself in these situations. At least One Piece sort of explains it with the whole fate theme of the manga (i.e. Luffy surviving his execution in Logue town) you should be grateful you have that. I dont see much difference in Rodger luck letting him survive in the Edd war as Luffy living through half his shenanigans
Maybe Rodger had it the same way as Luffy did. Based on what happened in the Edd war it seems probable. Either way I think you need to be much more than the strongest person in the whole world to be the PK; you need that combination of personality, strength, luck and fate on your side. It echos with what Whitebeard said to Blackbeard before he died about Blackbeard not being the person Rodger is waiting for.