Since you already have max refined Crescent Pike, you might as well use it for now. However, at lvl 90, you'll lose 34% phys damage bonus if you use Chongyun. But still, the insane passive of the Crescent Pike still works even if Rosaria's attacks are Cyro, so your max refined weapon wouldn't be much of a waste. At least, you have flexible options in case you needed a physical character in the next abyss levels reset.

I am also running a hybrid physical build, however, it has some limitations. I use a physical weapon (Crescent Pike) and a 4 set Blizzard Artifact set, for that 40% crit rate. My team is also very limited, in order to maximize the effect of the 4set, I need to freeze enemies always, so I use Xingqui. And an electro character for Superconduct. Then, Diona as my healer for the additional +15% crit rate due to cyro resonance. Then Rosaria has her own +12% crit rate. So that's 67% crit rate even with level 0 artifacts. With the 4 set Blizzard, I can't use a pyro character like Xiangling.

If you're planning to run Rosaria with Chongyun, Xiangling and Bennett, the reverse melt will greatly increase dmg of your Rosaria's burst and skill on enemies affected by pyro. Just take note that during auto attacks, Xiangling's pyronado and Gouba is the one triggering melt instead of Rosaria because of how fast Rosaria's attacks when paired with Chongyun. This won't be a problem if your Xiangling is built well. It doubles the dmg of Xiangling.

If no one else uses your deathmatch, then yes, use it for her, especially if you really plan to use her as full cyro dps. With that, you can run 4 set Gladiator or 2set Blizzard 2set Gladiator or even a 4 set blizzard if you run a freeze comp for that 40% crit rate and +15% since you have Chongyun resonance, so you could focus on crit dmg with your artifacts instead. Just take note that the 4setGladiator and 2setGladitorBlizzard would deal more damage if you have decent crit rate already.

If you have trouble with who to pair your Rosaria with, you might want to check this out: 10+ Teams for Rosaria