There is a list of predefined roles documented at - Users and Roles - Open Distro for Elasticsearch Documentation
The description says that - the security plugin includes several predefined roles that serve as useful defaults.
But this list contains a mix of static roles i.e. built-in roles created by the security plugin, and roles created by the sample config files at /usr/share/elasticsearch/plugins/opendistro_security/securityconfig/. If user does not use the sample configuration files provided by the plugin as-is, then those roles will not be available, but it would contain all the static roles.
On the other hand, for action groups, list of default-action-groups on the documentation lists only those action groups that are static.
It would be better if the documentation could be updated with a bit more clarity and only list the available built-in roles so as to avoid confusion.