This article offers an in-depth outlook on the development of C-V2X-based Intelligent Roadside Systems (IRSS), elucidating the applications and advantages of C-V2X in IRSS. It underscores how C-V2X enhances active safety by providing real-time traffic information, optimizes traffic flow through dynamic management, enriches information services for drivers, and facilitates autonomous driving by offering low-latency, high-reliability communication. The article examines the functional requirements of IRSS, including all-weather, full-element perception and highly adaptive local dynamic traffic organization, which are essential for the system’s robust performance. The system architecture of C-IRSS is designed to leverage the capabilities of C-V2X, which includes two communication modes: Uu for vehicle-to-cloud communication and PC5 for vehicle-to-vehicle and vehicle-to-infrastructure communication. These modes enable the exchange of critical data between vehicles, infrastructure, and cloud platforms, ensuring a comprehensive and coordinated approach to traffic management. The principles of tiered deployment for C-IRSS are also explored, with recommendations for prioritizing intersections with traffic signals, traffic guidance, or traffic control facilities in urban areas, and key nodes such as interchanges and service areas on highways. The article discusses the challenges faced in the large-scale deployment of C-IRSS, such as the need for algorithm generalization, the complexity of engineering deployment, and ensuring data quality and privacy.