Jeffery Black, 43, was arrested on Monday, South Salt Lake police said in a press release.
Black was reportedly in the car driven by Felix Anthony Calata on Saturday night, which hit and killed Romrell, who was responding with another officer to a report of a burglary.
Police shot and killed Calata on Saturday night. Calata had been investigated earlier this year in connection with a vehicular homicide case.
Black would be charged with homicide, burglary, obstruction of justice "and more," police said.