The song was written by David Paich, who has said that the song is based on numerous girls he had known. As a joke, the band members initially played along with the common assumption that the song was based on Rosanna Arquette, who was dating Toto keyboard playerSteve Porcaro at the time and coincidentally had the same name. Arquette herself played along with the joke, commenting in an interview that the song was about "my showing up at 4 a.m., bringing them juice and beer at their sessions." In the verses, the key is changed from G major to F major, accompanied on the original recording by the lead vocalist changing from Steve Lukather to Bobby Kimball. The drum pattern is known as a "half-time shuffle", and shows "definite jazz influence", featuring ghost notes and derived from the combination of the Purdie shuffle, Led Zeppelin drummer John Bonham's shuffle on "Fool in the Rain", and the Bo Diddley beat. The Purdie shuffle can be prominently heard on Steely Dan's track "Home at Last" from Aja, which Jeff Porcaro cited as an influence. The overlapping keyboard solos in the middle were created by David Paich and Steve Porcaro recording a multitude of keyboard lines using a Micro-Composer, a Minimoog, Yamaha CS-80s, Prophets, a Hammond organ, and a GS1, among other instruments. Paich credits Porcaro with both coming up with the concept for the segment and playing a majority of the parts. The album version starts with the drum beat only then kicks into the rest of the melody, then ends with two renditions of the song's chorus and goes into a musical interlude and fades out from there. According to Lukather, this final instrumental section was a spontaneous jam during the recording session: "... the song was supposed to end but Jeff carried on and Dave started playing the honky-tonk piano and we all just followed on." The single edit goes right into the melody at the beginning, then the song fades out during the first singing of the chorus at the end. Steve Porcaro and Lukather describe it as "the ultimate Toto track".
Music video
The West Side Story-inspired video was directed by Steve Barron and set in a stylized urban streetscape, with Rosanna represented by a dancer whose bright red dress contrasts with the gray surroundings. The band plays within a chain-link fence enclosure. Cynthia Rhodes is featured as the lead dancer Rosanna, which led to her being cast in Staying Alive the following year. It also featured Thomas Guzman-Sanchez of the dance groupChain Reaction as one of the male dancers. He did the Boogaloo/Popping body wave leaping over another dancer. Patrick Swayze can be seen as one of the dancers. Swayze and Rhodes later starred together in the 1987 movie Dirty Dancing. The video uses the album version of the song, instead of the single edit. Despite not playing on the actual recording, new bassist Mike Porcaro appears in the video, as original Toto bass player David Hungate left before the video was made. Lenny Castro is also featured with the band as a percussionist.
In 2018, American rock band Weezer released a cover of the track to poke fun at an attempt by fans to get them to cover "Africa", another song by Toto. Weezer went on to release a cover of "Africa" five days later.
