If you have issues with mp3 files/streams (internet radio station) in general you may have to provide codecs first.
You can try and convert the files into a different format or even mp3 again (with known good settings [you know this settings if you already converted to mp3 and the resulting files got successfully recognized by Roon]) to fix them.
You have my sincerest apologies for the delayed response here, we’ve been dealing with a higher-than-usual volume following our release and we’re working as quickly as we can to get back to everyone.
Following up on this thread, are you still running into issues with playback on certain files? @BlackJack has pointed you in the right direction for next steps. Please let me know if the above does not help