A JBoss Drools developer works on designing, implementing, and managing business rules and processes using the Drools platform. They create rules in Drools Rule Language (DRL) to automate business decisions, streamline processes, and improve operational efficiency. They also integrate Drools with other systems, debug and optimize rule execution, and ensure the system's reliability and performance. The developer also tests and maintains the rules, updates them as business requirements change, and provides technical support. They often work closely with business analysts to understand the business logic and translate it into Drools rules.