The commoner she wants to marry is also crucial. He represents the 'other' in the story, from a different social stratum than the villainess. Their interactions and relationship development are central to the story.
Another theme might be self - discovery. As she tries to marry a commoner, she may learn more about herself, her desires, and what truly makes her happy outside of the expectations placed on her as a villainess.
Well, in 'villager wants to save the villainess novel', perhaps the villager has a moral obligation that drives him or her to save the villainess. The story could explore themes like redemption. The villainess might have been misjudged by society, and the villager is the only one who believes in her innocence or potential for change. This could lead to an adventure where they face various obstacles together, both from those who oppose the idea of saving her and from the villainess's own past actions catching up with them.
I'm not sure about the exact plot as I haven't read it fully. But generally, it might be about Lady Rose's journey to become a commoner. Maybe she's tired of the noble life with all its rules and restrictions and yearns for the simplicity and freedom that commoners seem to have.
The villainess herself is often a popular character as readers are interested in her journey from being 'bad' to potentially 'good'. The male lead, who is usually involved in the villainess's romantic arc, is also popular.
One common theme is the transformation of the villainess character. Usually, she starts as a disliked or misunderstood figure but gradually changes for the better. Another theme could be romance. Often, there is a love interest involved that helps in the character's development.
Obviously, the villager and the villainess are the main characters. There might also be other supporting characters like the villagers who oppose the idea of saving the villainess, or some characters related to the villainess's past who try to stop the villager from his mission.
There could be antagonists too. Maybe there are powerful nobles or some self - righteous individuals who are determined to keep the villainess in her 'bad' position. These antagonists would create more obstacles for the villager in his or her mission to save the villainess. The villainess herself is also an important character. She may start off as a seemingly cold or mean person but as the story progresses, her true nature is revealed through the villager's efforts.
I'm not entirely sure as I haven't read it in detail. But generally, it might be about a lady named Rose who, despite her noble status, desires a simple commoner's life. Maybe she's tired of the strict rules and formalities of the noble world and dreams of the freedom and simplicity that commoners seem to have.