What did Roger do that everybody else did not that made him PK? He reached Raftel and after that, everybody called him PK. Now WB having the title of the strongest was not called PK. We can assume that you have to reach Raftel to gain the title of PK.
Now you interpreted about "the men Roger is waiting for" a bit wrong. He knows there's still a few men out there who could fulfill what he failed to do. So it's not that he waited for all of them, he just need any of them to reach Raftel. Though the more the merrier, just one D will suffice as long as he can fullfill what Roger couldn't. And it's very rare to find more than one D in a crew.
Now, those men and the of PK correlates to one another since both has to reach Raftel. The interesting part of this is that does reaching Raftel the only thing required to be PK? I don't think it is. There's more to that. I mean if BB and Luffy reached Raftel at the same time then both would be PK? What if another group reached it at another time? Will he/she be a PK?
Imo, there's something more to it that only a D can acquire. It's a bit cheesy but I think it's about how you gain friendship and bond to those people you've met in your journey to Raftel. After all those people/pirate are the ones who will decide who to them is PK.