<p>This study utilizes large eddy simulation to investigate the impact of train roll angles on aerodynamic performance, revealing that in the absence of crosswinds, the influence of the roll angle is negligible. However, under crosswind conditions, significant nonlinear effects on aerodynamic performance are observed. While the aerodynamic drag and side force coefficients show relatively minor sensitivity to the roll angle, the lift coefficient increases substantially as the roll angle rises, contributing to enhanced train instability. This increase in lift is primarily due to modifications in the flow channel beneath the windward side of the train during rolling motion. As the flow channel narrows, airflow velocity increases, generating higher negative pressure underneath the train; conversely, when the channel widens, the acceleration effect weakens, reducing the negative pressure. Importantly, the vortex structures remain unchanged with varying rolling angles, as the airflow separation point is unaffected by roll variations. These findings offer crucial insights into the aerodynamic behavior of trains under crosswind conditions, highlighting the need for design optimization to mitigate instability in practical situations.</p>