For
Rossi teams,
Camille is basically combining the role of
Wulfgard and
Akekuri. Heat Inflictions and buffs to increase Rossi's damage. All of this while also dealing some damage himself.
Mi Fu is also combining
Lifeng and
Endministrator utility in a single slot.
This enhances hybrid teams considerably, as all of these 3 units are supporting each other with their kit synergies. The last slot just depends on your preference and availability:
Chen Qianyu is the easiest option, as she's just there to apply vulnerable stacks efficiently. Camille generates a Link effect both on his Combo and the enhanced Skill after casting his Ultimate. When properly managed, this allows both Chen and Rossi to benefit from the Link effect.
Pogranichnik can carry
Thermite Cutter and apply Breach, which adds a lot of damage to Mi Fu's Crush. The extra SP generation also means you can spam skills more often, but it's unlikely you'll get enough Vulnerable stacks for multiple crushes in a single Breach.
Gilberta was the best recommendation for Rossi teams back in 1.1. And for a good reason. Sadly, the combo skill requires applying an Arts Reaction to enemies, which means you'll need to spend 100 SP on Gilberta skill (and hope it hits the enemy). She's still applying a massive Arts Susceptibility, which increases your Rossi's Ultimate damage a lot (maybe even Camille's Ultimate + enhanced Battle Skill), but for now she's better used in Mono Arts teams.
Example combo using
Chen Qianyu:
Chen Qianyu: Skill + Combo
Camille: Skill
Rossi: Combo
Camille: Combo
Mi Fu: Combo
Rossi: Skill
Mi Fu: Skill 2 + Skill 3
Mi Fu: Ultimate
Chen Qianyu: Combo
Camille: Ultimate
Camille: Enhanced Skill (Combo)- wait for Link
Chen Qianyu: Ultimate
Camille: Skill
Rossi: Combo
Camille: Combo- wait for Link
Rossi: Ultimate
Mi Fu: Combo
Rossi: Skill
Mi Fu: Skill 2 + Skill 3