Its true, if Luffy and Rodger had the same fruit powers SOMEBODY should have noticed it. And I also think its quite possible that Roger didnt have devil fruit powers at all.
I cant help but think of how it could be a similar situation to Naruto not knowing who his parents were. For some reason nobody ever slipped up by telling him. Maybe Oda is doing something like this to hide the fact that Luffy and Roger have the same powers. I can see how it would work. The good guys (Navy) wouldn't want Luffy to know bc that would most definitely spur Luffy on. That could be the Navy's MO. Second, it's been clear that information about Roger and his crew is pretty scarce. We are learning things about them as we go along just like the Straw Hats and much of the new Generation of pirates, and it would seem info on Roger and his crew is not common knowledge. Probably bc the Navy is out to suppress and even kill anyone that had anything to do with Roger. All in an effort to lessen the chance of another pirate king emerging. As for Shanks or Blackbeard or Buggy or any of the other pirates motivation for not telling Luffy, I have no idea lol.
Again, i may be reaching to rationalize the theory. Im not really adamant about either outcome. But thanks to the situation with Naruto and his parents I can totally understand how it could play out if its true. It is manga after all, and anything is possible! In the real world there is no way that Naruto doesn't figure out at least who his dad is, and that Luffy wouldn't know he had Rogers exact power. However this isnt the real world.
I cant wait to see how it plays out!!!!!!!! This is why I love One Piece!
