Yes I know it is not under Roll20's control, but one of our players has suggested that with a sound cloud account you can upload sound files and if you key word them so you can find them easily that should work. However, what sound file format must the actual sounds be, wavs or mp3's what exactly does Roll20 need.
One other question (I'm a gamemaster not a techno guy), could a sound be accessed thru a macro, so just a hit on a button could cause an Orc's voice to bellow, "Your balls will hang from my lodge pole" or something more colorful.