How does Gabriel's character and role change throughout "The Dead"?

Gabriel experiences painful personal growth at the end of the story. Through most of it, he is self-centered, seeing the world entirely from his own self-satisfied perspective. At the end of the story, however, he has an epiphany or awakening when he realizes his wife, Gretta, was in love with, and still thinks about, a young man, Michael Furey, who died years ago at age seventeen.

It is a shock to Gabriel that his wife was in love with someone before they met. He feels a sense of anger in having this dead lad as a rival for his wife's affections. Then his emotion turns to shame. At the Christmas party, he had been feeling good about himself and superior to some of his relatives, such as his aunts. Now he feels diminished. He thinks that:

While he had been full of memories of their secret life together, full of tenderness and joy and desire, she [Gretta] had been comparing him in her mind with another. A shameful consciousness of his own person assailed him. He saw himself as a ludicrous figure, acting as a penny-boy for his aunts, a nervous, well-meaning sentimentalist, orating to vulgarians and idealizing his own clownish lusts, the pitiable fatuous fellow he had caught a glimpse of in the mirror.

Gabriel also realizes that both he and Gretta are getting older. He looks at Gretta's face as she sleeps and realizes it is not a face a person would fall in love with anymore. He understands his own mortality too as he watches the snow fall, thinking about it falling on Michael Furey's grave. He realizes that:

His own identity was fading out into a grey impalpable world: the solid world itself, which these dead had one time reared and lived in, was dissolving and dwindling.

In getting outside of his ego in recognizing his wife has a life apart from him and in facing his own limitations and eventual death, Gabriel matures as a person.

Before the narrator provides the beautiful image of the falling snow, he tells us that Gabriel’s “own identity was fading.” One reason his identity “fades” is that he understands his wife a good deal more after she tells him her story about the man who had “died for her sake.”  His compassion enables him to merge with her rather than understand her only in relation to himself.  In other words, he learns empathy.  In this context, his “role” in their marriage changes (we surmise0 so that in the future he will be more humble and understanding.  In the context of the short story, he experiences an epiphany, enabling him to “see” more than he did before—this, too, suggests a change in role, from that of one who does not understand (which the reader perceives through dramatic irony) to one who does

At the beginning of the party, Gabriel feels he's better than most of the people there. He's better educated and considers himself more sophisticated. He thinks Ireland is a backward country with backward traditions, embarrassed that his wife is from a rural part of Ireland. His life is very controlled and organized, but he has never been in touch with his passions and emotions. His experiences at the party and his wife's innocent memory of a former love force Gabriel to examine his life and life in general. He has always thought that the past should be left dead and the present was for the living. Gretta's memory forces Gabriel to rethink this view. As Gabriel looks out the window and sees the falling snow, he's able to connect with the past when he sees the snow as "general all over Ireland". He realizes the snow touches both the living and the dead, and we're left with the hope that Gabriel will change his attitude and embrace life to be able to free himself of his routines and passionless existence.

How does Gabriel Conroy transform throughout "The Dead"?

Gabriel Conroy starts out smug, self-satisfied, and with a feeling of superiority to many of the people at the Christmas party, such as his aunts, to whom he condescends. He calls them ‘‘two ignorant old women.’’ While he is a somewhat timid and insecure person, he feels secure that his wife, Gretta, loves him and always has. He takes her love for granted.

Gabriel changes when, after the party, back in their room, he lusts after Gretta, but she is distant from him. He asks her what she is thinking and finds, to his shock, that she is remembering her former love, Michael Furey, who died young. Gabriel is utterly shocked that he is not the be-all and end-all of his wife's thoughts and feelings. He has to adjust himself to the idea that he is not the center of her universe and to incorporate the idea that the dead continue to live on with us in memory, perhaps more fully than the living. He ends up more humble and self-aware than when he started.

Joyce is very careful to present to us Gabriel's character as a man who is defined by indecision and worry. He is introduced as he tries to charm Lily, but fails drastically. He endlessly concerns himself with how he is going to be perceived by those around him, and debates whether he should include a literary reference in his speech or not in case it will make his New Year's speech too snobbish. He is unsure of how to respond to Miss Ivor's jibes and wants to make romantic advances to his wife, but does not know the best way to go about it. In short, he is so focused on appearances and his own neuroses that he forgets to really live in the full heat and passion of the moment.

What changes him at the end of the novel is the epiphany he experiences after hearing about his alter ego, Michel Furey, who, as his name suggests, lived life in its fullest sense. Note what Gabriel says to himself as he watches his sleeping wife:

One by one they were all becoming shades. Better to pass boldly into that other world, in the full glory of some passion, than fade and whither dismally with age. He thought of how she who lay beside him had locked in her heart for so many years that image of her lover's eyes when he had told her that he did not wish to live.

Gabriel suddenly realises that he has never really loved at all, nor has he lived life fully. He is one of those who, unless something changes, is doomed to "fade and whither dismally with age." He is granted the double-edged sword of self-knowledge, and is changed utterly as a result of this self-realisation.