User blog comment:Leman khan/Golden Belfry bell/@comment-3986064-20110729144352

The first reason that comes into my head is that, if he did, there would be no war for Luffy to stop!

But then something else comes to mind, Roger came there, only to visit Skypiea, he might've done nothing wrong and if no one attacked him or one of his crewmembers or friends, then why would he try to do anything, it would've been the same for Luffy, but Luffy got there at the perfect moment for the story, he didn't pay the fee, he was attacked by their police, Nami and the others were taken, he had to go after them, then he fought with whoever stood in his way to get to his nakama, but then he decided for them to look for gold... that was another link in the chain that made him stop the war. Also enel tried to destroy everything and eliminate everybody until he got to only 4 people...he took Nami, Luffy fought him to take Nami back, he failed, then Nami was saved by Usopp and Sanji, but Enel tried to destroy everything and he already injured and almost killed most of the SH! that makes Luffy angry and in the end he kicks Enel ass and he rang the bellfry to announce his friend from down bellow that Skypiea exists. Luffy stopped the war just because of this chain of events, not because he wanted to stop it, so he stopped it indirectly!

Roger had also like Luffy no wish to stop any war, he just came and left, but Luffy's case was a little special as you have just seen, hope this all made sense and answered your question