Use Readwise’s Markdown export to export data to Zotero for storage, then link the data in org-roam notes?
The problem remains that there is no option to sync between Readwise and Zotero or org-roam/Emacs, you would have to do it manually. I think there is an option for Obsidian but am not sure about this (I use neither). Exporting MD files from Readwise and storing them in Zotero does not make sense - you could directly integrate those files in org-roam. What I meant is that I replaced Readwise with Zotero and link to Zotero entries in Emacs (although I’m not using org-roam v2).
I’ve never used org-roam/Emacs and Zotero, thanks for the clarification. I’m using August Bradley’s PPV knowledge management system in Notion, which integrates with Readwise, but considering to migrate to Emacs org-mode; can Zotero sync with and provide spaced repetition to Kindle annotations/highlights like Readwise?
Interesting. Never heard of this, there are so many of these systems now 
. Zotero is for the organisation of academic literature. It also works well with most websites. But it is not at all a service like Readwise. There are packages for spaced repetition in Emacs but there is probably no working solution for Kindle excerpts.
Emacs and orgmode are fantastic and provide ultimate freedom to tinker and create your own system. But this way requires an investment in time and effort. And there is a scary learning curve. Given the details you provided so far, I would advise to use the systems/software you are already familiar with or to chose Obsidian. The search for the right tool only takes away time that you could spend on your topic. 
On this see also: Why not use Obsidian and/or Logseq instead of Emacs Org-Roam+Org-Mode? - #10 by laotang
Edit: Just watched the first eight minutes of August Bradley’s intro video. I don’t know how to better phrase this but his system feels like a distilled version of all pkm systems of the last few years. P.A.R.A., second brain, getting things done etc. Almost as if ChatGPT had put together something. Just an observation, if this works for you then please, by all means, continue.