Yusuf: He brings us to the dream: He opens the door with his key to bring us to the Dreamers.
He’s the Gatekeeper, Morpheus.
Mr. Saito: He’s the Samurai. Electricity, power his domain. He is order. He is omnipotent. He has at his command the entire real world. In the world of the dream where imagination rules, his earthly powers have no value. Here he is wounded, destroyed. Yet, his realism and hold on life are crucial to allow the dream to come to completion. If he didn’t hold on as tenaciously onto life as he does, the last dream wouldn’t be complete, the projections would stop Cobb and Ariadne from bringing Fischer back. He saves the dream and it is his power that returns Cobb to the natural order. The relationship is symbiotic: Without Cobb he can’t keep the world intact, without him, Cobb can’t return to an intact world. His goal of avoiding the creation of an empire, a mono-culture is so very close to the way that in nature no single species or organism can have the fully dominant role. As soon as a species threatens to overwhelm all other species a natural rebalancing occurs. Mr. Saito’s role is to ensure that this rebalancing, the inception, the creation of a new idea, a new phase in evolution occurs.
Eames: The forger, his “specialty” is “references”. He’s Loki, the Trickster, the maker of connections. He creates metaphors, finds ways of translating from one realm to another. On his own he’s not much good: He doesn’t have the drive or the mission to bring about inception. Without him, without his wit and brilliance, an endeavor like Inception, which requires “Imagination” is impossible to achieve.
Arthur: He’s order, “specificity”, his mission is to create the structure that allows the dream to transition, he controls the transition from reality to dream by maintaining the outside structures required to let free reign to imagination inside. He, literally, ties up the loose ends and brings it all together. He’s the one who maintains the Dream inducing machinery. He’s the Engineer to Ariadne’s architect.
Robert Fischer:
He’s the inner child. The wounded self that is looking for validation. Inception shares the rage against the distant father with Kafka, Spielberg and Lucas. Fischer is the Luke Skywalker, the hero who’s journey allows us, allows Cobb to regain faith. His emotional catharsis, when his father returns his individuality to him, is the trigger to Cobb’s release: If Cobb succeeds with inception, with making Fischer his own man, he will “go home” to “his kids”. In the course of the story, Fischer moves from “child”/being kidnapped to “waking”/learning of his illusions to “making his own choices”/acting to discover the truth and gain validation. Of all the characters in the movie, his role is the most symbolic and the least self sustained. Where with any of the other characters you feel a sense of purpose and self-interest, he seems to be entirely devoid of purpose except to lead us through the journey and to give us our own catharsis. It is remarked somewhere that the actor, Cilian Murphy has had a bag placed over his head in the last three films he shot with Nolan. The symbolism couldn’t be more clear: The child is being held prisoner, is hiding. Until it emerges, until the boy becomes the man there can be no whole. The way to becoming a man then isn’t through hardship and suffering. The way to become a man is to receive validation, in a dream or in reality, of one’s own worth and power.
Mal:
She’s the symbol of Love gone out of proportion. Mal, as in malignant is the deformed shape an emotion takes when the source was overpowering. Just as the image of the overbearing mother can remain so strong in a child’s mind that it overpowers healthy relationships and emotions, so can the love of a wife who demands the ultimate sacrifice become an image that is too strong to overcome. Losing her and blaming himself for her loss is the “Guilt, guilt, guilt” that Cobb feels, that keeps him from allowing the Inception to complete. Mal sabotages Cobb every step along the way. What he perceives as his love for Mal, his eternal devotion, becomes a vicious circle trapping him in a debt he had no need to pay. Mal “had herself declared sane by three independent psychiatrists”. Thus it must be Cobb who’s not sane. Rather than allow himself to destroy the perfect image he’s created of her, he’s willing to forsake his release, his catharsis and return to normality. Because of what they built together, what she signifies to him, he can’t let her out of his life, even though her presence is no longer needed for him to continue.
So in our lives do we often refuse to let go of what has become our emotional normality, whatever situation, parental love we’ve come to know as good. Only when the wounded self (Fischer, shot by Mal) can no longer function, can no longer move towards independence can we choose to free ourselves from the burden of Mal’s poisoned love.
Ariadne:
Is the one who ultimately leads Cobb to his own freedom. She’s the one who see Mal’s negative influence. She is the pure spirit of Cobb’s gift and talent. Where Cobb has let the “basement” prison of Mal’s anger trap him and rob him of his gift to dream, Ariadne’s free to discover creativity and to create a pure dream. She is strong enough to confront Mal and to protect Cobb from his attachment. Her motives are pure, she acts selflessly and has compassion for Cobb. She is the saint, the savior and the pure spirit that stands on the other side of the conflict that Cobb faces between creation and destruction, between letting an idea become a cancer that destroys and giving an idea away freely to allow the self to be. She “kills” Mal to protect Cobb. Her act is not done against Mal, it’s done for Cobb. She sees what is right and in doing so, she frees everyone from Limbo: Cobb can make good on his promise to Saito, Fischer can move forward and discover his emotional release. Her action is to “cut the Gordian knot”. She refuses to see a dilemma in Cobb’s choice of “changing memories” and “growing old with Mal”. Cobb doesn’t have to stay with Mal and live his life to be “an old man, filled with regrets”.
Cobb:
He’s the Dreamer and the dream. Mal challenges him if his reality isn’t like a dream, chased around the globe by giant corporations. And throughout the movie he questions his reality, uses Mal’s totem to establish what’s real and what’s not. He clings to Mal’s definition of reality. Her love that is poisoning him is irrefutable because she’s the one who established his values for reality. His brilliance, drive and determination allow him to create the plan that will bring Fisher to his truth and restore him on his path. Yet, it’s only after Ariadne creates his release that he can free himself and return to his life and his children, knowing in his memory now that there was a way for Mal’s love to be whole and for them to live old together. All that happened was that in their lives they couldn’t. So instead of regretting a past he can’t have, he learns to focus on a future, the children, that is there. Mal’s “murder”, his guilt over losing her was what was keeping him from returning home. He had to do something to change that situation. There was a way that required letting go of his perception of her: He says that he can’t imagine her with her perfection, with everything she is. In other words he retained the painful emotion that had overpowered his life, when the relationship was so much more than simply this emotion. In order to let go, to become himself, he had to descend three layers into the dream and let his “child” his innocent self discover his true worth.
That’s my 2 cents . Not sure it’s worth that much…

Ariadne is French. In French, the Bishop is called Fou, or Fool, Arcana 0, which depicts a character obliviously walking toward a cliff’s edge. But Ariadne’s Fool plunges forward, like should Cobb who is repeatedly instructed to make a leap of faith.

And Mal: The only name this could plausibly be a diminutive for is Mallory, which means “ill fated”, “unfortunate”.