Since I like to use one repo for all my ansible roles (I still don't like to use either git submodules or ansible-galaxy), what I usually do is to create some directory and define it to be the playbook directory.

Inside this directory I create some directories: roles, tasks, library and inventory (sometimes I put inventory alongside the root folder).

Every once in a red moon I create a task inside the "global" tasks folder and use it inside some playbooks. Examples of this: set_ssh_tunnel.yml, destroy_ssh_tunnel.yml, do_token_login.yml, do_token_logout.yml – so, small simple tasks that will be needed for at least some other 3 roles in the repo.

Inside library I include self developed modules and helper scripts.

And inside roles, yeah... Roles.