You could easily argue that "The Road Not Taken" by Robert Frost relates to every piece of fiction: every novel, every short story.
At its heart, the poem is about considering your options in life, wondering what will happen when you make one choice over another, and looking backward to see how your choices have made irrevocable changes in your life. It also seems to be about the choice of when to follow the path that others have taken (when to do what's expected of you, or do what your parents have done) and when to branch out and make a new decision, venturing into unknown territory. (Of course, a few dissenting voices do claim that the poem's message is darker than that, even opposite to the idea of free will. Please refer to this essay for an example.)
So, since every work of fiction deals with characters making choices that impact their lives, "The Road Not Taken" can be easily linked to pretty much every story ever written.
Let's apply it to The Namesake, then. Look for the places where the narrator, Gogol, has to pause and consider before making a choice. Where does he realize that he can't have things both ways, that he has to choose? When does he look backward to reflect on how his choices affected his life?
I'd focus particularly on these places:
1. Gogol chooses to reject his Bengalese heritage, even separating himself from his family.
2. Affected by his father's death, Gogol decides to reunite with his family.
3. Gogol must make a choice about how to handle his increasingly tense relationship with his American girlfriend.
4. Gogol must choose what to do about his interest in Moushumi, the traditional Bengalese woman he is falling in love with.
In each of these places where Gogol's life "diverged in a yellow wood," so to speak, he must choose which "path" to travel, whether or not he ends up recalling his life with a sigh in old age, like the speaker of the poem does.