Explain how the father/son roles in "Night" were reversed in the case of Elie and his father?
Elie's father protects him and sacrifices his share of rations in the beginning of the novel in order to keep up Elie's strength. As physical strain, the cold, and illness wreaks havoc with Elie's father, Elie steps up and takes the more protective role. He arranges things with deals and trades in order to stay in his father's work group and to be near him. Elie shares his rations with his weakening father.
Although it is clear that Elie is becoming less and less "human" through his suffering...going so far as to outrun his father in one of the group's movements and hoping not to find him when his guilt spurs him to half-heartedly go looking...he never completely forsakes his father and the link between them as father and son. He regularly visits the window at the hospital to speak with his father until the day that Elie is told his father was taken that day. Even when his father dies, Elie is not without emotion although the situation does not allow him to grieve properly.
Without a doubt, Elie is forced to grow up much faster than he would have in a normal childhood situation. His is similar to children whose parents are chronically ill, disabled, or who succumb to illegal substances and are unable to care for themselves...they are all robbed of their ability to be "kids" and moved into "caregiver".
Elie leads, and his father, Chlomo, follows his son's lead throughout most of the book. He urges his father to persist, even when Chlomo is ready to quit. Towards the end of the autobiography, Chlomo becomes quite ill and cannot take care of himself at all. Elie assumes an even greater parental role and urges medical attention for his father; he keeps his father fed and hydrated as best he can. Elie continues to care for his father until the older man dies.
After they leave Buna, Elie becomes strong and forceful with his father. Chlomo is weakening, not able to withstand the cold conditions or the physical strain. Elie pushes him forward, encourages him and supports him to keep Chlomo alive and walking. When his father becomes ill, Elie manipulates things in order to stay near him. Chlomo despaired, but Elie was his strength - more of a father than a son.