Role-based addresses are typically company addresses defined by a job rather than a person, and are often managed by several people or eventually fall into disuse. Some of these types of addresses are associated with high bounce rates and spam complaints, so Mailchimp blocks them from your import. Role-based email addresses also cannot be used to sign up for a Mailchimp account.
Subscribers with role-based email addresses can still join your audience. It's only during an import that these are blocked.
A new subscriber with a role-based address should use your signup form to subscribe. Share your signup form link with that potential subscriber, so they can opt in to your audience.
If you have express permission to add a role-based subscriber to your audience, add them as a single subscriber.