Is it possible to disable CSS and Javascript aggregation by role?
To do exactly what you want; using hook_css_alter &amp; hook_js_alter is how to do it. Set the preprocess key to FALSE for everything.

For an out of the box solution that is fairly close to what you want https://www.drupal.org/project/advagg/ can do it. Give that role the "bypass advanced aggregation" permission and then they can add ?advagg=-1 to the end of the URL to see the change.

Will also mention that using a dev environment when altering css/js is ideal.