A Composite Applications developer designs and develops software applications that are composed of different functional units, known as services. These services, which can be developed using different programming languages, are integrated into a single, unified application. The developer's role involves understanding business requirements, designing the application architecture, coding the services, and ensuring they work seamlessly together. They also troubleshoot issues, optimize performance, and maintain the application post-deployment. This role requires expertise in SOA (Service Oriented Architecture), knowledge of various programming languages, and strong problem-solving skills.