At about 1.4 metres (4.6 ft) long, H. rossicus was the largest species of Hesperornis and among the largest hesperornithines, slightly smaller than the large Canadian genus Canadaga.
Dug oko 1,4 m, H. rossicus je bio najveća vrsta u rodu Hesperornis i među najvećim hesperornitima, neznatno manji od kanadskog roda Canadaga.