{% assign textbox = thing.textbox %}

<ul class="list text-roller text split sml">
  {%- for item in textbox -%}
  {% assign custom = item.title | replace: '&','and' | downcase %}
    <li class="item text-roller {{ custom | replace: ' ','-' }}">{{ item.title }}</li>
  {%- endfor -%}
</ul>

<ul class="list text-output sml">
  {%- for item in textbox -%}
  {% assign custom = item.title | replace: '&','and' | downcase %}
    <li class="item text-output {{ custom | replace: ' ','-' }}">{{ item.text }}</li>
  {%- endfor -%}
</ul>