Themes and plugins must add their own version into CSS/JS files, e.g: style.css?ver=x.x.x
For 404, I don’t really see why it will generates this issue as the new path of the CSS / JS files is updated once WP Rocket is cleared.
I don’t think we will do this automatic suggestion: clearing CDN cache after clearing WP Rocket.
Why? It will result to huge increase of bandwidth usage on CDN, and it will have an impact on your cost.