Roam is way of using a wiki. i.e. you could quite easily set up a wiki to act in much the same way as Roam.
The journal part of Roam, the page-per-day part, is very useful. You write down what you're doing each day, use tags and links to build up a second brain, so to speak.
Let's say, today I'm working on kubernetes. I add a tag for k8s, which is a link to the k8s page, where I have all sorts of interesting links and notes dumped. When I'm on the k8s page, I also get a list of pages that link to the k8s page, which helps me to remember some other subject that might be relevant.
It uses the Zettelkasten Method: https://zettelkasten.de/posts/overview/ and you can also get a lot of value from reading "How to Take Smart Notes" by Sönke Ahrens.
The value also comes from it mirroring your thoughts and experiences, as I said, the second brain thing.
(I'm terrible at explaining stuff, sorry :( I hope I didn't bore you to bits)
