In general, I stick all my shared roles in a single master folder that gets shared across all my projects. This avoids the tediousness of manual copy/pasting and updating multiple copies of the same role.
Than I modify each project's ansible.cfg to tell ansible to look for roles in that master folder in addition to the local project folder.
Sample ansible.cfg:
[defaults]
roles_path = ~/Code/ansible_roles
Ansible first searches the local project for a role, then searches the roles_path. You can specify multiple paths by separating them with colons.
By default, ansible-galaxy install username.rolename will install the role to the roles_path configured in ansible.cfg, so that's pretty much all you need to do.
Occasionally I want to install the role into the specific project and not the master folder. For example, to avoid version conflicts when two roles have role dependencies that require different versions of the same role. In that case, you can use the -p ROLES_PATH or --roles-path=ROLES_PATH option:
ansible-galaxy install username.rolename -p ~/Code/project_deploy/ansible/roles/
In Ansible 1.9, you can manually specify where you want a role to be installed in your project's requirements.yml. Unfortunately, this path param was removed in Ansible 2:
# from galaxy
- src: jeffwidman.elasticsearch
# from private github repo, installing to a relative path
- src: https://github.com/jeffwidman/private_ansible_role
path: vagrant/roles/
If you want to customize things further, there's an open issue to add support for multiple ansible.cfg files which would let you easily set roles_path at varying levels of specificity. Ansible will read ANSIBLE_CONFIG, ansible.cfg in the current working directory, .ansible.cfg in the home directory or /etc/ansible/ansible.cfg, whichever it finds first.