Structuring Ansible playbooks for low volume, purpose-built images
Unless I totally missed your question, roles are exactly what you need in this case. I'll use examples from my real world. My code below is just to illustrate my point (so it is not fully runnable, might contain errors and is not bullet proof rocket science: you will probably have to adapt/overcome tools limitations). But at least you'll be able to tell me if I got you wrong.

Let's say your servicing a large community of developers on different techs: java, php, nodejs, scala, python, ruby... needing some tools as well like apache, nginx, postgres, mysql, redis...

You have a role for each of these techs/tools, and possibly use existing ones from galaxy that you don't even have to write and that you can download at provisioning time. These roles can possibly be controlled with vars to choose e.g. versions. (see vagrant provisionner config below)

Now, one way you can activate/deactivate roles in a play is with the use of tags

Your unique playbook could look something like this

- name: Vagrant provisionning playbook
  hosts: all

  pre_tasks:
    # whatever you need to do before roles

  roles:
    - role: php
      tags: [php]
    - role: java
      tags: [java]
    - role: nginx
      tags: [nginx,php] # if you always deploy php with nginx
    - role: redis
      tags: [redis]
    # more roles here

    tasks:
      # Whatever tasks are needed to be played after roles


With such a structure, you can now configure your ansible provisioinner in vagrant defining the tags and specifying the vars needed to provision with your single playbook.

Vagrant.configure(2) do |config|

  config.vm define "php_application" do |php_application|

    # Some config for vm
    php_application.vm.provision "ansible" do |ansible| 
      ansible.playbook = "playbook.yml"
      ansible.tags = "php,nginx,untagged"
    end

  end

  # Host vars declared globally. You might be able to do
  # it on host by host basis but the doc does not specify it
  config.vm.provision "ansible" do |ansible|
    ansible.host_vars = {
      "php_application" =&gt; {"php_version" =&gt; "7.2"}
    }
  end
end 


Does this fit your needs ?

Note: if a single playbook is too much of a hassle, you can still use the roles and assemble in each playbook the techs/tools you need and reuse things that you will need in several places.