"Riojasaurus" had a heavy body, bulky legs, and a long neck and tail. Its leg bones were dense and massive for an early sauropodomorph. In 2010 Gregory S. Paul estimated its length at and its weight at . By contrast, its vertebrae were lightened by hollow cavities, and unlike most early sauropodomorphs, "Riojasaurus" had four sacral vertebrae instead of three. It has been thought it probably moved slowly on all fours and was unable to rear up on its back legs. The nearly equal length of the fore and hindlimbs has also been interpreted as suggestive of an obligatorily quadrupedal gait. However, in 2016, Scott Hartman found the hand anatomy, relatively straight back and largely immobile shoulder girdle of "Riojasaurus" supported it being a biped.