Phylogenetic analysis has shown that Romaleodelphis is most closely related to other odotontocetes previously grouped together as the "Chilcacetus clade, now a paraphyletic grade basal to true dolphins and beaked whales.

The holotype skull of Romaleodelphis was discovered in 1980 in the sediments of the Ebelsberg Formation during the construction of a hydroelectric powerplant near the town of Pucking, Upper Austria.

[1] The name Romaleodelphis derives from the Greek "'romaléos" meaning sturdy or robust, in reference to the strong zygomatic process of the squamosal bone, and the -suffix "delphis".

[1] The phylogenetic analysis conducted in the type description of Romaleodelphis recovered 15 most parsimonious trees, the strict consensus of which showing that the animal was a derived toothed whale.

The PCA also suggests that some early members of Platanistoidea fall into the same morphospace, likely representing yet another example of narrow-band high frequency hearing arising independently among toothed whales.

Whatever the case, the anatomy of the semicircular canals in Romaleodelphis suggests that the hearing was more sensitive to head movement than in Xiphiacetus and porpoises, as inferred based on comparison with certain baleen whales and the bottlenose dolphin.

Since narrow-band high frequency hearing is not associated with any biome in particular (dwarf sperm whales are pelagic animals that inhabit the open oceans, porpoises stay close to the coast and the La Plata dolphin even swims up estuaries), Sanchez-Posada and colleagues speculate that it is possible that Romaleodelphis could have theoretically been capable of traveling between fresh-, salt- and brackish water.