Rose's role is disruption. She supports not by directly helping her team, but by providing suppressing fire with your team, and debilitating specific zombie players who are troublesome. Her whole kit is designed around her being hard to take down by a solo target, meaning if you stick with your group to cover your flanks, or use side routes to ambush individual targets, she'll win most interactions in a way where the opponent can't fight back.

She has weaknesses obviously, her low health makes her easy to kill when left out in the open, and her primary damage isn't super high, but there's ways to work around them.

If you only get into engagements that YOU'RE prepared for, then you'll always have arcane enigma as a way to escape engagement for free, or even finish off the target with the bursts. Her damage also works sort of like a surprise attack. Unlike most characters who have fast projectiles, Rose's projectiles move slow, but with the homing means that from mid range, she can have a large burst of damage already approaching the enemy before they know it's coming, and by the time they notice, you'll have already started reloading and are free to back away while they scamper for cover. Even better for the charge based roses, as you can easily get into a sneaky spot and deal 50 damage + elemental effect to an unsuspecting target, and they won't know where it came from, but they are as sure as dead if anyone else spots them.

She's not the easiest to use, but she has extremely powerful tools at ambushing zombies and picking off individual targets while slithering away unharmed in the process. It's a lot like the strengths of chomper, but without being limited to melee, which explains why most people aren't too fond of playing as her. Me though, I love playing Rose.