These include the multicuspid teeth of characoids, unicellular epidermal horny projections (named “unculi” by him) in most groups of ostariophysans, and recurrent trophic polymorphism of the lips, horny jaw sheaths, and other soft mouth structures of the Cyprinidae.
His Systematics, Biology, and Distribution of the Species of the Oceanic Oarfish Genus Regalecus (Teleostei, Lampridiformes, Regalecidae), 2012, is the authoritative publication on the subject.
It is unparallelled in its scope, detail, documentation and shrewd scientific reasoning, as well as providing some challenging hypotheses, also in connection with climate change and the Gulf Stream, while at the same time very accessible for the interested reader.
In this major study of the fascinating longest bony fish ever (Guinness Book of Records), Dr Roberts has scrutinized all the material available worldwide and throughout history, even taking into account geological evolution over millions of years, a colossal undertaking.
Roberts's other scholarly interests include Charles Darwin and his concept of natural selection as products of the Scottish Enlightenment, and identification of royal portrait statues of ancient Khmer devaraja or divine kings with the reigning monarchs they portray including Suryavarman II and Jayavarman VII.