This pattern is used to provide a quick way to include multiple roles at once. For example if you have a group of things that every server needs, you could use a meta role to include those things with one line.
So lets say you have three roles for every machine named
logs_to_syslog_server. You can include them all by making a role named
common. In that common role you make a file named
meta/main.yml and put the following contents in it.
--- dependencies: - role: users - role: ssh - role: logs_to_syslog_server
The on every host you simply add the common role.
roles: - role: common tags: [common]
and suddenly you get all the common roles. You can also run with
-t common to run all the common rules. This is handy if something global to your infrastructure is updated and you would like all hosts to receive the update.