Reddit reviews Roots of Evil (AD&D: Ravenloft Adventure RM1)

I just finished CoS a few weeks ago... easily one of my favorite campaigns. I loved the old 2nd edition stuff and had all the supplements and all the novels. I loved all the little references to the characters and family lines I knew from the novel I, Strahd (which is a fabulous book to read if you haven't already; I, Strahd: The War Against Azalin is also worth it).

So! I didn't want to leave this place either. My players are returning soon with new characters 150 years after the events of the story involving their old characters. I want them to see the long-term changes their old characters made, like how they restructured the leadership of Vallaki. Across the realm, they new characters will explore the changed terrain while the players will be able to recognize the marks their old characters left behind.

You can easily go this route, but there's another option, too, if they're set on keeping these characters. Look up an event called The Grand Conjunction. My memory isn't perfect, but I'm sure there are plenty others in this sub and similar subs that can help you out. Basically, you had to stop the realm of Barovia from bleeding into the Forgotten Realms plane and unleashing its evil upon its inhabitants. The borders of the Ravenloft realms shuffle and open, and other realms like Nova Vaasa, Forlorn, and Borca, join Barovia to form the Demiplanes of Dread properly. There's a 6-book adventure set that culminates in Roots of Evil. This page can tell you more; scroll down to section II.