Roll20 has a number of resources available in its online shop, though surprisingly not as many as a competitor like Fantasy Grounds can offer. What Roll20 lacks in content of this nature is made up for by inherent flexibility; you can run just about any game with it so long as someone takes the time to craft a character sheet for you.
As it happens, since it looks like my regular group will be gaming in Roll20 for at least the rest of May and (with any bad luck) June, I decided to investigate the rulebook compendiums on offer for Pathfinder 2nd edition. Worth noting right off, there is a way to link up your Paizo account. When you do this, it immediately gives you some decent discounts on the Roll20 rulebooks. The $49.99 rulebooks, for example, are $38 when you do this. I have only ever bought these books in PDF format from Paizo before, so I don't know if proof you bought a physical copy generates an even better discount.
I started with the book that had the most obvious potential at the virtual game table: The Bestiary for 2E. It was available immediately on unlock, and proved to be a wealth of immediately accessible resources. As a GM, here's what the purchase netted me of immediate and great use: all of the Bestiary monsters in the Compendium, each with the ability to pull standard stat blocks/text of their descriptions, as well as an NPC sheet format that lets me "one click" any action or ability to generate relevant rolls and ability block details. You can also drag and drop to create the icon for the monster, and basically gain roughly all the perks a player has on their end, but for your monsters.
The Bestiary for 2E on Roll20 is the full content of the print book, too. If you do not own it in any form, but planned on gaming only through Roll20, then you will find this book does everything you could want (except detach itself from Roll20). For some gamers, this may be more than enough. I know that just having this content loaded and ready makes it much likelier (and easier) for me to stick with Pathfinder 2E as my virtual system of choice.
I next loaded the Core Rulebook and the Gamemastery Guide. The intrinsic value of these tomes is slightly more ephemeral. You get the ability to directly reference and share content with your players, and you gain entries with full "use at the table" properties for the many magic items, relics, artifacts, NPCs and other details....but with the caveat that prior to loading them the base Roll20 game still gave me the 2E OGL content to reference anyway.
Additional content includes official NPC and player tokens and lots of compendium details on the many special optional rules in the Gamemastery Guide. Both books in total feel very complete, but I think as a GM on a budget you could ignore them and stick to the print or PDFs and not feel like you're missing out. Since I happened to have the cash it was worth it, but if you could only buy one tome, the Bestiary will provide the most traction.
One downside to Roll20 is that while it does offer the rules tomes, it seems to be way behind setting up the Adventure Paths. I am guessing that no one in the VTT business anticipated that in March of this year they would suddenly be the #1 resource for gaming across the country. My understanding from digging around online is that Roll20 does the VTT adaptations and they are way behind; this is a shame, as whether you ran the modules straight up or not, those would be great additional purchases for the compendium, since there's lots of useful content in the modules you can use as-is or pilfer for your own purposes.
Anyway....the price of entry for VTT compendiums is a bit on the pricey side, and you can use Roll20 just fine with print or PDF books. But, if you want the full luxury experience and every official iota of Pathfinder 2E at your fingertips, then the compendium books are a nice addition to your virtual collection. I may cave and get the Starfinder books next.