A Java Beans developer designs and implements reusable software components in Java, known as Java Beans. These components are manipulated visually in a builder tool. The developer ensures that the Beans adhere to conventions, including having a zero-argument constructor, being serializable, and properties being accessible via getter and setter methods. They also incorporate events, properties, and persistence in the Beans. The developer's role involves troubleshooting, maintaining, testing, and improving these Beans. The aim is to create highly reusable and portable components that can be manipulated to suit different programming needs.