Which files can reasonably be shared, and which not? How should you share them and use them?
Roles, tasks, and modules are the Ansible files that you can easily share. They should not contain anything specific to a particular environment or deploy. Use variables where necessary, with reasonable defaults if possible, to allow a play that uses them to customize their behavior. Use facts to make them work on a wider range of host types.
Inventories, playbooks, and group and host variable files are where the information specific to your environment or deploy lives. These can't readily be shared.
The main mechanism in Ansible for re-using files from
elsewhere is the configuration variable :ref:`roles-path`.
This lists other directories that will be searched for
roles directories after the local roles directory.
How you get the additional roles directories' content is left up to you. For example, you might just copy the files there from somewhere else, or network mount a filesystem containing them, or check them out from some version control system, etc.
An important thing to consider is controlling changes to shared files. If you just set things up so you're always using the latest versions of the files, and someone makes a change to the shared files that breaks your deploy, then your deploy will break the next time you try to use it, and you will not be able to deploy again without fixing your files to be compatible again.
It's much better if your deploy uses a very specific version of the shared files. Then you can choose when you want to switch to a newer version of them, test the changes, and always go back to using a version that you know works if you need to. In other words, there will always be a way you can get to a working deploy system if you need to.