Any custom playlist created by you can be deleted from your user account. Note: you cannot delete playlists created by another staff member.
From your web portal via dashboard.rockbot.com, follow these steps:
Click the Music Icon (left sidebar) > Click "Add Playlist" > Click "My Music" (top tab) > Select the playlist you'd like to delete > Click "Edit Playlist"
From the view that allows you to see all of the songs in the playlist, click on Edit.
Scroll until you see the Delete Playlist button. Keep in mind, once you delete the playlist it will be completely removed and there is no way to recover it after it's been deleted.
You can also view all of your playlists directly here.