yep, pcpete bet me too it
it sounds like you need to open up the roadrunner config program and in the Music section on the left, there will be an option somewhere to specify the file types. Click the button and a list will come up displaying many 3 letter file extensions (mp3, wav, and others among them) and just click each one until you have all the ones selected that you want. After that, click the "Done" button and save your config file. At this point you should be able to open up roadrunner and have all of your music display
Hope this helps!