title: Execute only one role in my runlist
body: <p>In my run list, I have two roles</p>
  
  <pre><code> "run_list": [
      "role[web_server]",
      "role[web_client]"
  ]
  </code></pre>
  
  <p>I want to execute only one role for some nodes and another one role for some other nodes. How to do this? Is there any idea to put some condition over there? I dont want to change my runlist. I have this run list common for all nodes. but I want to execute one role for few nodes and another runlist for few nodes.
  Any suggestions?</p>