A CSS/SASS developer designs and improves the visual layout of websites or web applications. They use CSS (Cascading Style Sheets) and SASS (Syntactically Awesome Style Sheets), a scripting language that interprets into CSS, to control the look and feel of web pages. They manage color schemes, typography, responsive design, and overall aesthetics. They also handle cross-browser compatibility issues and optimize front-end performance. They collaborate with UX/UI designers and web developers to ensure the functionality and efficiency of the web interface. They also maintain style consistency across different web pages and elements.