The Roma River is a river located in the Empire near the northern borders of the Kingdom of Elbe, flowing from its source (based on the map included in the manga) near Alnus, as well as from a tributary sourced in the Tuba Mountains east to the Blue Sea. The city of Deabis is located along the river. The Roma River is navigable at least as far as Deabis, and sees a large amount of traffic consisting of boats and small ships sailing up from the Blue Sea.
The river is home to a race of aquatic Humanoids possessing both fish-like tails and humanoid legs. This race was first encountered by the Japan Self-Defense Forces when they were crossing the river as part of an attack on the Flame Dragon.