I think Anki is great at learning specific facts, even quite complex ones—I have used it extensively to learn languages—but it doesn’t offer any opportunities to link ideas together. It’s basically an efficient method of taking facts—even complex facts like “what does this sentence mean?” or “what did people say in this short video clip?”—and putting them sufficiently into long-term memory that you can then use them in the real world. This final step is crucial as it allows these Anki facts to come alive and become much richer as they become part of rich semantic web.
Anki offers no possibility of linking up and developing ideas. It’s basically a very efficient memory device.
Roam might be great for writing papers etc, but is it a long-term solution for note taking? Who owns your data? What happens when the company goes away?