Rosie manifests in the back of a bus and immediately kills the recently awakened driver, stealing his clothes. She then seeks out Sherman's assistant and hides in the back of her car, later killing her as well. The next day, Rosie enters Sherman's practice, coincidentally at exactly the same time as Cameron. Being bound for the same location, they both enter a lift and share a look with each other, taking note of the other's behavior. Upon arriving at Sherman's door and simultaneously reaching for the handle, Rosie and Cameron immediately realize that they are fellow cyborgs.
Cameron struck first, initiating a fight between the two, which at first appeared to be an even conflict, but Cameron quickly established her superiority over Rosie. The fight took them back into the lift where Cameron tried to dislocate Rosie's arms, but she proved to be remarkably flexible and was able to overcome Cameron's forced contortions. The fight came to an unexpected halt, however, as both machines sought anonymity in the presence of humans. Once they were gone, they resumed their fight, resulting in Cameron forcing Rosie to the floor, who tried to retaliate by wrapping her legs around Cameron.
Cameron turned this against her, however, and forced Rosie's own heel into her left eye before proceeding to contort her body in such a way that she was no longer a threat. Cameron then broke her neck, effectively cutting off power from Rosie's power cell to her CPU. Cameron would later try to remove Rosie's chip, only for it to self-destruct upon removal, a new feature for Terminators that suggests Skynet's desperation to prevent reprogramming in the future. In the season 2 finale Catherine Weaver discovered that chips were covered with phosphor that inflames when contacted by air during extraction. Possibly Rosie's chip was protected the same way.
While her Series and Model number remain unknown, Rosie appears to be no more advanced than the average T-888, though like Cameron, she suffers in physical confrontations due to her petite form. One interesting observation, however, is that Rosie possesses a remarkable flexibility of movement, being able to contort her body in ways so far unseen in Terminators, although this may have been more so a result of Cameron's attacks breaking her body. However, she is also capable of easily fixing dislocations to a certain degree and possesses the self-destruct chip modification  in case her chip is forcibly removed and to prevent reprogramming. Rosie's chip also bears some similarities to Cameron's in terms of outward design, which alongside the similar build may imply that she is actually a T-900.
It is unclear if Rosie was either an agent of Skynet or the future Resistance as it is also unclear as to what her mission exactly was. There are several possible assignments:
- Mission: Terminate Dr. Boyd Sherman. [This scenario assumes she is acting as an Skynet agent.]
- Rosie may simply have been programmed to be more inconspicuous in her duties, and therefore took a pure infiltration approach to her mission as opposed to walking in guns blazing. This is the more likely scenario, seeing as how it is revealed in "Born to Run" that John Henry's purpose is to develop into an Artificial intelligence advanced enough to fight Skynet.
- Mission: Terminate John Conner. [This scenario assumes she is acting as an Skynet agent.]
- Skynet may have been aware of Dr. Sherman's association with John Conner, and decided to take the opportunity to strike when Cameron and Sarah would be unlikely to interfere due to them not being allowed near John during his sessions with Dr. Sherman.
Mission: Protect Dr. Boyd Sherman. [This scenario's assumption would imply either way.]
- Rosie actively seeks out and terminates Sherman's assistant, presumably with the intent of taking her place. This is hinted at by Sherman himself when he tells John that the "agency" has sent a replacement, only for Rosie to arrive several minutes later.
- Further support can be deduced from the fact that Dr. Boyd Sherman is killed shortly after the events of "The Tower Is Tall But the Fall Is Short" in "Strange Things Happen at the One Two Point". Assuming that Dr. Sherman is killed in both timelines, it would be more likely that her mission was not to kill him. Because of her self-destructing chip, she was most likely sent back by Skynet. Her mission may have been to either prevent him from dying or for pure infiltration and information gathering, both of which would be of benefit to Skynet. On the other hand, keeping Dr. Boyd Sherman alive might be in the interest of the future Resistance and worth protecting by Rosie; hence, a positive benefit to them. When Cameron terminates Rosie in the elevator, this would imply more complicated ulterior motives are in play and at work. Who would benefit from Cameron's action is unknown.
- Mission: Get close to John Connor. [This scenario assumes she is acting for the future Resistance.]
- Since it is known that Dr. Boyd Sherman is a person of interest on Sarah's wall list, Skynet may believe that Boyd Sherman is somehow involved with John Connor, and therefore the future Resistance may be trying to replace his assistant and get closer to John Connor to protect him.
- Rosie's name is not mentioned in the actual episode, but appears in the closing credits.
- Her name could be an homage to Rosie the Robot from The Jetsons.
- There was some confusion concerning Rosie's name early on, leading to her being called "Victoria" by mistake for a time.
- Terminator: The Sarah Connor Chronicles
- It is stated in "Born to Run" that the self destruct modification is a phosphorus coating of the chip that reacts with oxygen if exposed to the air.