I heard somewhere that in every generation there are 36 just people because of their righteousness G-D allows the world to continue. Is this true? Why 36? How are these people identified? What is their role, obligations, how are they different than others in the eyes of G-D, in receiving reward of Olam Haba and anything else relating to this topic.
There is a talmudic tradition (Sanhedrin 97b, Sukkot 45b) that in the merit of the 36 righteous in each generation the world survives. There is no authoritative explanation for the various questions you raise. Possibly 36 is double 18, which is the numerical value of twice life. Chai - life is het = 8 and yud = 10. The letters for thirty asnd six are lamed vov meaning "His" indicatuing complete devotion to his will. The 36 according to many traditions are secret, not identified. It is common when one wants to say that a person to say someone is a great zaddik to say "He/She is a lamed vovnik" meaning one of the thirty six. This is a metaphore.