As far as I know they never introduced a system or method to allow uploading copyrighted music that you’ve purchased the rights to. Roblox Staff told me to message them and they’d help me take care of it, but they eventually ghosted me. So unless something has changed, there isn’t a way to get around the automatic copyright removal system if a song is auto flagged.
@buildthomas said they would introduce a proper pipeline for this in the future, but it’s been almost three years… I might have missed the feature if they added it though? I’d love to be able to use the music I paid hundreds of dollars for!