Question.

Say I have the bought the guides for certain games and they are downloaded to my hard-drive in PDF form. Could I still use them in my games in Roll 20 and use them as basis for character sheets? Or do I have to use the market place? I really do not want to hash out money for a game I have to buy twice. 

u can set up a game, the game, in roll20 and use the roll20 character sheet for it, without buying the book on here

Thanks. got a little confused for a moment. 

best way to see it is, go ahead and click "Create Game" you'll see the choice of Char Sheet for that game

Peter, Roll 20 is a virtual table top, providing tools, apps, and an interface to run and play RPGs. The market place is a convenience but is not necessary. While you can use your own material you would need to put your own game together using the resources provided by your subscription level. The more canned or put together you want your game to be, the more you would likely purchase through the marketplace. It's possible to not purchase any material or assets from Roll 20, but you then need to put everything together yourself.