The thumbs up/down buttons are for adding / not adding a song to the upcoming queue. It’s maybe not the best visual metaphor for that. You can build up an upcoming queue by clicking it repeatedly and if you know a song and don’t like it, don’t add it by clicking thumbs down.
There’s a pop you get when a song is playing and you skip it, there you can tell Roon why you skipped it.
That’s a tiny input to the Roon algorithm, so you won’t screw up anything for yourself forever if you do that.
Here’s a discussion with info by Roon staff on how this works: