rodauth-oauth supports the translation of all user-facing text found in templates and error messages, by integrating with rodauth-i18n. Just set it up in your application and rodauth configuration.
Instructions are available in rodauth-i18n README.
rodauth-oauth ships with translations for all its default user-facing text. These can be found here.
Changing a translation is a matter of overriding the key in your own locales file.
If your intended language isn’t available, consider having the text translated from english, and contribute it back to the repository.