"Rosie" is the leader of the demolition team working for Damien Darhk.
In 2016 she and her two partners, Jackhammer and Hardhat, were ordered by H.I.V.E. to take out SCPD captain Quentin Lance. They lured him to a building with a fake phone call. When he arrived they used explosives to collapse the building. However Quentin was able to escape the building with the help of his daughter Laurel.
At their hideout they then got attacked by Team Arrow. Rosie and her team managed to hold them off and she destroyed their laptop after she and Hardhat activated an explosive to destroy the building and then escaped.
They then tried to destroy a building where debates for mayoral election were held and received direct order from Ruvé Adams not to let Oliver Queen leave the building alive, which they failed due to intrusion by Team Arrow. Rosie fought Black Canary and Speedy and ended up being knocked out.
- Expert combatant/Martial artist: Rosie was able to fight Thea and Laurel simultaneously for a long time before she ended up knocked out.
- Explosives expert: Rosie can destroy buildings with great precision. During combat she and her team use small explosives. 
- Nailgun: Rosie uses a nailgun as her primary weapon.
- Explosives: Roise uses an assortment of explosives to destroy buildings.
- Screwdriver: Rosie was seen using a screwdriver to install the explosives.
Behind the scenes
- In the DC comics Rosie is also a leader of a mercenary group named the Demolition Team. Her look in the comics is referenced in the series, as both in the comics and in the series she wears jeans.