It might be possible to play private sounds from soundcloud without Roll20 having to know how to log in as you. I uploaded something and made it private. Then on the screen for the sound there is a secret link. This is sort of like how private works with Youtube. A private video on Youtube no one can ever find through a search, but if you give them the link they can play it. So I can play the sound with the secret link when I'm not logged in to sound cloud. So then I went to a campaign in Roll20 and searched for my sound using the secret link. Roll20 found the sound and even displays it properly, name and waveform. But no sounds come out. You can even add it to your jukebox, but it still doesn't play. So it might just be some small tweak a Roll20 dev would have to do?