Similar to Mega Man, Roll was created by Doctor Light as a utility robot, albeit one intended for more feminine tasks such as housekeeping. Her name is a nod to that of her brother, as together their names are "Rock and Roll."
Unlike Mega Man, Roll was not given any combat upgrades when Wily prompted the Robot Masters to rebel, and hence, stayed home to cheer on her brother. Unlike many female game characters of the time, however, she has rarely been captured.
Compared to her brothers, Roll does not have any apparent powers besides the usual abilities of a robot. However, she is an able fighter, demonstrably capable of fighting hand-to-hand, or with various weapons. She occasionally carries a portable version of Mega Man's plasma cannon, although it is weaker and is not built into her arm, and she also has proven adept at using random objects as melee weapons. In particular, she is partial to using brooms or mops in combat.
Compared to Mega Man, Roll has made less appearances in the other branches of the series, but she nonetheless recurs in some of them. Versions of Roll are not present in the X, Zero, ZX, or Starforce eras, but the following two are:
In the 81st Century, the Casket family travels along with Mega Man Volnut in search of useful archeaelogical artifacts. Unlike her original counterpart, this Roll is not biologically related to Mega Man, and is potentially his girlfriend.
This is Roll's counterpart in the Battle Network series. Similar to Roll Casket, she is Mega Man's friend and potential romantic interest, corresponding to her operator Mayl Sakurai, who is the girlfriend of Lan Hikari, MegaMan's operator.
According to series creator Keiji Inafune, she was originally intended to be playable in Mega Man 2, but as he felt a female character may have alienated the mostly-male audience of video games, this idea was ultimately dropped. As attitudes towards women in video games changed, she came to take part in more of the action. She is a playable fighter (along with Mega Man) in the first two Marvel Vs. Capcom games, and was also playable in both the cell phone and PSP remakes of the first Mega Man game. Most recently, she has appeared in Tatsunoko Vs. Capcom.