Ability to upload Custom Roles via CSV Merged

While trying to upload users via CSV Import option, it does not carry out the task of adding users with ‘Custom Roles’. The upload works fine with standards roles (Viewer, Reviewer, Contributor), but fails to perform if user needs to be added with any Custom role [Contributor (Product Owner (Contributor)) , Contributor (Product Owner (Integration)) etc.]

Please look into it and advise if there is a possibility to accommodate Custom roles also with CSV Import.