Sorry, it was probably a bad word choice. What I meant was that it is up to you to take all the module's information and put into Roll20 yourself; i.e., you will have create all the maps, tokens, characters, and handouts from the module in Roll20.
Yes, it is a lot of up front work, but that's the nature of VTT gaming. However, another tremendous asset of Roll20 is ability to copy a campaign. This is an excellent feature if you want to set up a written module and run through it several times with different PCs. As an example, I have coded/written the AD&D module N5: Under Illefarn into Roll20. I then copied the campaign before it has been played. In this way, I can play through the module with my current group, but I also have a pristine and untouched copy of the module to use if I want to run through it again with a different group of PCs and players.