Which characters are central to Der Rosenkavalier?

The central characters in Der Rosenkavalier, a comic opera by Richard Strauss, include the following main vocal parts:

• The Marschallin: The wife of a field marshall, sung by a soprano.
• Octavian (Count Rofrano): The Marschallin’s young lover, performed as a mezzo-soprano "trouser role."
• Sophie von Faninal: A young woman intended to marry Baron Ochs, sung by a soprano.
• Baron Ochs: The Marschallin’s crude and overbearing cousin, sung by a bass.
• Herr von Faninal: Sophie’s father, a baritone.

The opera is notable for being dominated by its female vocal parts; because Octavian is the lover of the Marschallin and the suitor of Sophie, the majority of the work's love music is sung by women. The final trio featuring these three characters is considered one of the most famous passages in the opera.1