can someone state 3 roles of religion in Pi's life and long journey on the boat?

Part One details Pi's three religions; check out gradesaver's summary linked below;

http://www.gradesaver.com/life-of-pi/study-guide/section2/

The section below comes from gradesaver's analysis of the novel's themes;

Belief in God

Belief in God is clearly a major theme in Life of Pi, and has been the most controversial in reviews of the book. Throughout the novel, Pi makes his belief in and love of God clear—it is a love profound enough that he can transcend the classical divisions of religion, and worship as a Hindu, Muslim, and Christian. Pi, although amazed by the possibility of lacking this belief, still respects the atheist, because he sees him as a kind of believer. Pi’s vision of an atheist on his death bed makes it clear that he assumes the atheist’s form of belief is one in God, without his realizing it until the end. It is the agnostic that truly bothers Pi; the decision to doubt, to lack belief in anything, is to him inexcusable. This is underscored in that essential passage in the novel when Pi asks the Japanese officials which of his two stories they preferred—he sees no reason why they should not believe the better story.

Pi’s devotion to God is a prominent part of the novel; it becomes, however, much less prominent during his time aboard the lifeboat, when his physical needs come to dominate his spiritual ones. Pi never seems to doubt his belief in God while enduring his hardships, but he certainly focuses on it less. This in turn underscores the theme of the primacy of survival.

Thank you but could you have the 3 major roles pointed out in your own opinion?