Research efforts are underway to understand the inherent surface roughness in additive manufacturing (AM) particularly in powder bed systems. It has been acknowledged that powder bed systems may suffer from layer variation due to sputtering effects or recoating mechanism. This lack of layer uniformity has negative effects on surface roughness. This research investigates the effect of layer variation on minichannels surfaces through which fluids flows for heat transfer applications. For this, a number of long stainless-steel flow channels with various cross sections were fabricated using selected laser melting technology. In addition, an experimental setup was developed to measure the pressure drop for different gas flow rates. This study provides insights into the relationship between surface roughness deviation along minichannels length and the pressure drop in the flow minichannels.