While sitting in with L.A. punk group DC3, members of Black Flag heard her playing, which led to her being asked to join Black Flag to replace founding member Chuck Dukowski. Roessler was majoring in applied engineering at UCLA, and Black Flag's subsequent tours were worked around her school schedule, which was a condition for her to join the band. Her bass playing was featured on five of Black Flag's studio albums. She remained in the band until completing touring behind their album In My Head in the autumn of 1985, then graduated from UCLA in 1986.
After Black Flag, she formed the two-bass duo Dos with Mike Watt (to whom she was married between 1987 and 1994), who are still performing today. She wrote or co-wrote songs for what would be the Minutemen's final album, 3-Way Tie, and to Watt's post-Minutemen band Firehose. She later contributed artwork to Watt's first solo album, Ball-Hog or Tugboat?.
On January 6, 2011, thieves broke into Roessler's home and stole, along with other items, a custom-made 3/4-scale bass made for her by California luthier Mark Garza. Fans and friends launched an online campaign through blogs, Twitter, and Facebook to help Kira recover the stolen instrument, which she retrieved ten days later after the thief attempted to sell it at a Guitar Center.