A rolang is like a zombie. This is a human being whose body is alive but who is neurologically and psychologically paralyzed to the degree that he or she functions like an automaton.
"Wade Davis wrote a book (The Serpent and the Rainbow, 1985) in which he tried to demonstrate that Haitian zombies are people who have been poisoned first with puffer fish poison and then later with datura. They are then kept in a brain-damaged state and sometimes used as laborers. To be zombified is said to be a "fate worse than death" reserved for those who have offended community norms.
I know that Haitian culture is far from Tibet, however, datura does grow
in the Himalayan regions and is one of the symbols of and traditional
offerings to Mahakala (Dorje Gonpo). If I remember correctly, the ancient Scythians in central Asia inhaled datura fumes in a ritual context. Perhaps Tibetan rolang are people who have been brain damaged by deliberate or accidental datura poisoning who revive after being in a coma. [So] Believing in zombies may not be so irrational after all. [And] It would make killing them a non-meritorious act.
A friend of mine who was in Tibet two years ago said that people he knew took the existence of rolang for granted and said that the high wooden thresholds of Tibetan houses were to keep them out as they cannot bend their knees. "
~ R. Bunger (personal communication, ca. 2000)