I've been milling about something for a bit now.
Upon Roger's death 22 years from the current time in the storyline, tons of pirates sprang up seeking fame, glory, and ultimately his treasure of One Piece. But according to several accounts, there have been pirates around as early as fifty years or more, sailing the Grand Line and the other seas. We know of Brooke/Yorki's crew, Shakky and Raleigh's Crew, and I'm sure there are many others out there. The number may have increased thanks to Roger, but the concept of piracy was nothing new.
So here's my question: By giving the pirates a common goal, has Roger effectively aided the Marines/WG? Granted, because of this influx, the Shichibukai were created, but the pirates are all heading toward the same place: New World, Raftel Island. Since they follow a set course to said Island, it's safe to assume the Marines can track any pirate they want. Look how easily Kuzan found them once he knew what route they were on. Smoker, on the other hand, had to guess, but once he found the mayhem at Whisky Peak, he knew they were headed for Arabasta.
Look at Moria, even. Kuma was able to find his ship almost instantly, which says a lot about the Marines' ability to track their targets.
Was that Roger's plan? Or do you think it was accidental? I've always had a theory that Roger could have been a former Marine that had a change of heart and became a Pirate when he discovered something, but you never know with Oda. Oda's only predictable in one thing, and that's friendly character death.