entity_register.yaml
###
media_player.kok:
  config_entry_id:
  name:
  platform: cast
  unique_id: d10e088a-d912-3e33-ab99-d0a40de8ded7


scripts.yaml
###
  radio538:
    alias: Play Radio on Chromecast Audio
    sequence:
      - service: media_player.volume_set
        data:
          entity_id: media_player.sovrum
          volume_level: '0.75'
      -  service: media_player.play_media
         data_template:
           entity_id: >
            {% if is_state("input_select.chromecast_radio", "Sovrum") %} media_player.sovrum
            {% endif %}
           media_content_id: >
            {% if is_state("input_select.radio_station", "P4 Sjuhärad") %} http://http-live.sr.se/p4sjuharad-mp3-192
            {% elif is_state("input_select.radio_station", "Lugna Favoriter") %} http://fm03-icecast.mtg-r.net/fm03_mp3
            {% elif is_state("input_select.radio_station", "Bandit Rock") %} http://fm02-icecast.mtg-r.net/fm02_mp3
            {% endif %}
           media_content_type: 'audio/mp4'


configuration.yaml
###
input_select:
  radio_station:
    name: 'Select Radio Station:'
    options:
      - P4 Sjuhärad
      - Lugna Favoriter
      - Bandit Rock
  chromecast_radio:
    name: 'Select Speakers:'
    options:
      - Sovrum
      - kok
    initial: Sovrum
    icon: mdi:speaker-wireless