The false accusation
The irony of the false accusation is that Rose is such a good person that she goes out of her way for the whole novel to do the right thing, and in the end, the irony is revealed to the entire cast. Instead of being a murderer, she is a sacrificial lamb for the kingdom, taking a bullet for the throne. Her reputation throughout the book is ironically opposite of her true nature, pointing toward a reversal of fate some time in the future.
Dramatic irony and rescue
The dramatic irony of the plot can be summarized in the character of Dimitri, because he is on the outside of Rose's hero's journey looking in. When he rescues her, that celebrates the dramatic irony of Rose's serendipitous survival. Instead of Deus ex Machina, Rose depends on those who understand her and want her to succeed, so in a way, she has saved herself by being a good person in her community, and by earning their continued support. They are her heroes, and she is their hero.
The dilemma of self and community
The hero's journey that Rose endures is one of individual growth and transformation, because her character is dynamic and evolves through the plot, but in a much more important sense, her story is the story of a community. Her heroism is ironically community oriented, which makes her well-qualified to succeed because her motives are pure. She loves others, so she is willing to change and evolve, like the alchemist's metals.
Community destabilization
The ironic selfishness of Tasha Ozera is that she wants to be in charge of people, so she tries to usurp the throne, but if she had succeeded, her reign would be terrible. She is not motivated by community, but by power, so her attempt to kill the queen is a symbol of her ironically poor qualifications for leadership. She doesn't love the community, but is willing to upset the balance to get what she wants. No one in the story is less worthy of power than the one who wants it most.
Self-sacrifice
The irony of Rose's self-sacrifice, besides the reversal of her reputation (she was known as a queen killer, but she ends up being a queen savior), is that she willingly accepts death for someone else. The reader will notice her love for her community, which is certainly part of the sacrifice, because the queen represents the authority that keeps the community in lawful order. By sacrificing herself for the queen, she lays her life down for everyone she loves.
