The plot of the live-action "Dragon Ball Z" movie, "Dragonball Evolution," involves Goku attempting to stop Piccolo from obtaining all seven Dragonballs. On his journey, Goku is joined by allies such as Bulma, Yamcha and Roshi.
In "Dragonball Evolution," Goku, played by Justin Chatwin, is an ordinary high school student. After attending a party hosted by his crush, Chi-Chi, played by Jaime Chung, Goku returns home to find his house destroyed by Piccolo, played by James Marsters. Piccolo has also mortally wounded Goku's grandfather, Gohan, played by Randall Duk Kim, who tells Goku to seek out Master Roshi, played by Chow Yun Fat.
Goku sets out on his journey, and soon meets Bulma, an employee of Capsule Corporation played by Emmy Rossum. They soon track down Roshi, who begins training Goku in the use of ki, a mystical energy that fuels martial arts. After recruiting Roshi to their cause, the group runs into a trap set by Yamcha, a desert bandit played by Joon Park. Bulma convinces Yamcha to join the group, for a price, and they all eventually track down Piccolo, who kills Roshi in battle. Goku then destroys Piccolo with the Kamehameha, a powerful ki attack, and avenges Roshi's death. The group then uses all seven Dragonballs to wish Roshi back to life, ending the film.