Retroperitoneal sarcomas (RPS) are characterized by a predominant progressive- pattern of local recurrence, making radiotherapy a cornerstone of adjuvant management. Advances in radiation delivery—such as image-guided radiotherapy, intensity-modulated radiotherapy and proton therapy—have significantly enhanced therapeutic precision, enabling improved tumor targeting while minimizing collateral damage to adjacent tissue. This review investigates the value of perioperative radiotherapy for resectable RPS, focusing on the indications, efficacy, and technical optimization strategies. Studies indicate that preoperative radiotherapy significantly improves local control rates, with varying efficacy across histological subtypes, whereas the benefits of postoperative radiotherapy remain controversial and require careful risk-benefit evaluation. In addition, we explore the potential advantages of intraoperative radiotherapy and hypofractionated regimens, as well as forecast the future prospects for integrating radiotherapy with systemic therapies, aiming to optimize RPS management and improve patient prognosis.