Sorry for the nitpicky question, but I have always used and seen in both printed and digital song names ( ) used much more than, [ ] for both actual song names and remixes, but for some reason Roon almost always uses [ ]. This is possibly something I can change in the settings somewhere, but haven’t been able to find it…
Am I the only one?
If you add the album to your library then you can alter song titles.
One by one 
Indeed. No other way, as far as I know.
Yes, I know… but that’s quite a daunting task, although I have done it already more times than I can count already. Was hoping for a better solution.
Roon takes its track listings from AllMusic, as far as I know. The square bracket preference comes from them, not Roon. Having said that, I’m in total agreement that square brackets don’t look great.
It’s inconsistent in the Roon default track titles, wherever they come from.
I change all such round parentheses to square brackets because parentheses occasionally occur as regular parts of song titles, e.g., Neil Young’s Hey Hey, My My (Into the Black), but square brackets are very rare in actual titles and are IMHO better suited for additional information.
There really should be a preference or bulk change feature.
If you are using a tagger, like Yate for Mac, you can make global changes like the ones you wish. This would only apply to local tracks. Qobuz or TIDAL tracks would have to be changed one by one.