I am relatively new to Roll20 too. Got the legendary bundle on D&D Beyond. I feel you pain, but they are two totally different entities. If you brought a season ticket to watch films in one chain if cinema, it does not give you the right to watch films in a different chain of cinemas. This is no different. One campaign I am running the adventure is almost at an end. I could buy it on Roll20. But with the expectation of finishing it soon I have simply grabbed a few of the maps from Beyond, pulled them into Roll20, and created a few tokens in Photoshop. Set up a few handouts, and all is good. Allows me to grab the immediate benefits of Roll20 without buying the adventure again. Second campaign is in early stages, so worth my while investing in a copy on Roll20. I could manually drop the material from Beyond to Roll20, but the rime it would take, the cost to buy again is a worthy investment. With both campaigns I have the added benefit if utilising Beyond as a reference source whist mobile. It also gives me a solid encounter builder (when needed) and a superb reference tool for rules. Roll20 gives me a digital table top, dice roller, etc which is years ahead of what Beyond currently offers. The message here is enjoy what both has to offer. Take advantage of the strengths each has over the other, and use them side by side.
