I own a game, do I have to buy roll20's copy?

I own a copy of The Quiet Year, I want to start a campaign on Roll20 of this game. Is it allowed to use my copy instead of buying roll20's version of the game? I'll admit I am tempted to do so, as it would make playing easier on this site. I already own a copy though, and don't really want to buy another one; especially one that can only be used on this site which costs more than I payed for mine. I just want to use my copy and not get reported or kicked off the site because I am using a personal copy of the game. Can anyone help me with this?

You can host games for whatever game you want including uploading scans, images, etc.... As long as you aren't trying to sell it.

to reiterate what Jason said, you can use your own materials for your own games, you don't have to buy the ones that Roll20 offer.  They are a convenience and time saver.  Similarly, owning your own physical copy or digital copy from another source doesn't save you from the cost of buying the Roll20 one if you want the Roll20 one.

The one you can buy on Roll20 is pretty nice, mainly because it comes with the 4 card decks already set-up for the seasons Spring, Summer, Fall, Winter. They are set up on the Card Decks feature of Roll20. You can make your own decks if you want to spend the time, but it is a 1-card-at-a-time process to remake it yourself. Buying it on Marketplace mainly just saves you from recreating all those cards in Roll20 (which you are allowed to do in your personal game, no problem, that's just playing the game on your own tabletop).  The Roll20 version also comes with the "Rules" again, however, that part doesn't save you much time from just reading/explaining the rules to players verbally anyway. I recommend buying it for the cards set-up, or implementing it yourself as a manual Card Deck making process to get set-up. Either way, it is fun to use the Roll20 whiteboard tabletop for collaborative drawing / mapping, as The Quiet Year encourages.

Thank You so much I was legitimately worried about this. I may at some point buy the Roll20 version, but for now I will use what I have. Thanks so much!!

You don't have to buy anything if you don't want to.