Due to their partnership, Roll20 has access to all of Paizo's content, but Roll20, not Paizo, are in charge of what is made available and when.
when will paizo finish adding pathfinder 1st edition and starfinder adventure paths to roll 20? yall made this huge announcement about the partnership and lil to nothing has come of it. meanwhile DnD has all their stuff added to roll20 pretty much shortly after launch if not at launch.Just to be clear, Paizo (and Wizards) are not the ones adding content to Roll20; the Roll20 team determines the pacing of their content releases.
I'm pretty sure that Roll20 also controls what they charge for the content and what discounts are offered. I believe that there is a discount if you already own the PDFs and sync your Roll20 account with your Paizo account.
A Roll20 Community Manager posts periodic updates in this thread. Looks like the latest news is that they plan to have Extinction Curse available this summer.