This study explores how a Business Process Management (BPM) driven Robotic Process Automation (RPA) approach supports sustainable process design in omnichannel retailing. In a controlled experiment, Business Process Management (BPM) orchestrates workflows while Robotic Process Automation (RPA) executes tasks, with as is and to be processes (AS IS/TO BE) modeled using Business Process Model and Notation (BPMN). Two representative cases, order routing and real time inventory updating, are implemented. Performance data are compared with a manual baseline across four indicators: execution time, execution mode, service readiness, and manual involvement. Results reveal substantial gains, including faster processing, a shift to real time execution, continuous service availability, and reduced human tasks. These improvements lower errors and reconciliation needs, strengthening supply chain responsiveness. By mapping the outcomes to Global Reporting Initiative (GRI) standards and interpreting them within the Triple Bottom Line (TBL) framework, the study demonstrates contributions not only to operational efficiency but also to the economic, social, and environmental dimensions of sustainability in the omnichannel context.