Beyond Happy Days, Kelly reprised her Pinky role on the first episode of the short-lived 1977 Happy Days spin-off, Blansky's Beauties. She had a small but memorable role in the television thriller Curse of the Black Widow. She portrayed Diane Sullivan in the slasher film New Year's Evil (1981). Kelly also played guest roles on Starsky & Hutch, Match Game '76, The Paul Lynde Halloween Special, Baretta, Kojak, The Love Boat, The Dukes of Hazzard, Charlie's Angels and Fantasy Island. Her role in Starsky & Hutch was created when star Paul Michael Glaser (Starsky) planned to quit at the start of the third season, with Kelly's character, Officer Linda Baylor, intended to fill his place. However, Glaser was persuaded to stay, and Kelly's character ultimately only appeared in one episode, "Fatal Charm". Her characters on these other series never reached the level of cult fame that Pinky Tuscadero gave her. So closely identified was she with the character that she was billed as Roz "Pinky Tuscadero" Kelly for her appearance on The Paul Lynde Halloween Special.

On November 29, 1998, she was arrested for firing a 12-gauge shotgun into the living room window of a neighbor's house after a car alarm woke her up; she also shot the neighbor's car and another car nearby. The neighbor was not home at the time. She pleaded no contest to the charge of firing into the house and was sentenced to three years' felony probation on October 20, 2000. Kelly was also ordered to receive psychiatric counseling and pay restitution as ordered by the probation department.

On October 27, 2000, she was sentenced to 120 days in jail after pleading "no contest" to charges stemming from an August 20, 2000, arrest for hitting a man with her cane. She was given credit for the 98 days that she had already spent in jail awaiting sentencing, thus avoiding having to spend any more time in jail.

On Happy Days, Kelly played Carol "Pinky" Tuscadero, the older sister of Leather Tuscadero (singer Suzi Quatro). Just as Arthur Fonzarelli insisted on being called "Fonzie" or "the Fonz", Carol insisted on being called "Pinky", and usually dressed in attire to match. Pinky was slated to be Fonzie's long-term girlfriend after her initial appearances in episodes #64–66; commercials for the next season even began promoting Kelly's new character. When discord occurred among Kelly, the cast and producers, her character was dropped; she was only mentioned briefly in two later episodes.