Auth0 is a company not an authentication protocol and so from that point of view you need to talk to them about what they support. However, a simple internet search suggests that they support the OAuth protocol which Roundcube 1.5 will support. The Release Candidate of Roundcube 1.5 was published a few days ago and so you might want to give that a try, assuming you know the OAuth config information for you AuthO account.
