<p>Periodic rolling waves, resulting from dynamic variations in liquid film thickness, are critical to the hydrodynamic and particle transport behavior that governs spiral concentrator efficiency. This study investigates the effect of wall roughness height (<i>K</i>s) on these dynamic characteristics using both hydraulic theory and a VOF numerical model. The findings reveal a non-monotonic relationship: as <i>K</i>s increases, the amplitude and frequency of the rolling waves first decrease and then increase. Crucially, this paper is the first to identify and describe a “velocity oscillating region.” This phenomenon is driven by rolling waves. In this region, the liquid's radial velocity periodically changes in both direction and magnitude. The spatial extent of this oscillating region in the liquid's surface layer similarly decreases and then expands with increasing <i>K</i>s. As <i>K</i>s rises further, this oscillating region spreads to the liquid's bottom layer. The presence of a suitable oscillating region induces intermittent jitter in the particle layer, which is conducive to particle stratification and segregation. Conversely, an inappropriate oscillating region may significantly alter particle migration trajectories, impacting separation performance.</p>