A software architect plays a crucial role in system design by defining the technical structure and standards for a software project. They ensure that the system meets both functional and non-functional requirements, balancing aspects such as performance, scalability, and security. Their responsibilities also include making high-level design choices and recommending appropriate technologies for implementation. The architect collaborates with development teams to maintain a cohesive vision throughout the project lifecycle, often addressing complex problems that arise during the design or implementation phases, ultimately ensuring the success of the system architecture.