Rossa has brown eyes and a relatively slim figure, but much shorter than Fisica and Ritmo. She has red hair with a ponytail and wears a cloak similar to Ritmo's, but brown. Like Fisica, she wears earrings infused with Notalium to protect against Al Niente. She has a brown shirt & a brown belt with jean shorts. She wears brown boots with a buckle halfway down.
She doesn't show much of an outgoing personality, as she doesn't take time to get to know Fisica or Ritmo when they first meet. She treated them coldly until Fisica saved her from a falling rock in Chapter 3, Section 3. Even after this, she only said "......Thank you."
Rossa relies heavily on her wits to get through situations, which is a sort of facade that she holds up pretty well. The only time this was broken was in Chapter 3, Section 3, when Fisica saved her from a falling rock. She was dumbfounded at Fisica's kindness, and was at a loss for words.
Although she, typically, acts cold and enigmatic, she has a more childish side that seems to come out when she is interrupted by her partner, Nero. When Ritmo asked who her and Nero were, she said, "It does not matter who we are," but Nero then said, "Her name is Rossa." To this, Rossa complained, "Hey, don't reveal any information unnecessarily, Nero!" in the Chapter 3 Introduction.
Although she doesn't speak much, when she does, most of the time, it'll contain purely factual information, rarely voicing her own opinion when it has to do from a situation that's not completely logical.
- Fisica - Not particularly unfriendly toward, and when they first met, Rossa was trying to stop her and Ritmo because she was told that they were "hostile." She started thinking more of Fisica as a friend after she saved her from a falling rock in Chapter 3, Section 3, and even apologized later in Section 6 about the prior unfriendliness with a more refined apology. In Section 4, Fisica asked learn more about the 'outside world,' she said, "No problem."
- Ritmo - They, mostly, only interact when she's speaking to both Fisica and Ritmo at once, but she seems to be slightly more snappy toward Ritmo. In the Chapter 3 Introduction, Ritmo asked, "Who are you two exactly?" To which she replied, "It does not matter who we are," but this is the only personal interaction the two have. She, most likely, started to bond with Ritmo after the incident with the falling rock in Chapter 3, Section 3 like she did with Fisica. Aside from that, it can only be assumed that she thinks of him similarly to how she thinks of Fisica.
- Nero - Her work partner for an unknown duration. Mostly, she talks to him at a professional level, as they theorized with each other after every time Ritmo tuned. When Nero interrupted her in the Chapter 3 Introduction, she got slightly irritated at him, suggesting that they have been working together long enough that she can act casual around him.