Harold Meza, 26, is claiming former Roberts staffers Glynnis Vaughan and Diane Porter have filed claims against the supervisor that, among other things, called into question his relationship with Meza.
Eight people have resigned from Roberts' office since he took office in January 2013. Ex-scheduler Diane Porter recently filed a claim against the county that contends the supervisor made her work on political activities during work hours and spend office money on campaign materials, and created a hostile work environment, particularly for women.
Porter also accused Roberts carrying on an inappropriate relationship with Meza, pointing out a hotel stay.
According to the suit filed by Vaughan, the supervisor misused county funds and created a hostile work environment.
Roberts has denied the allegations.
Roberts is a freshman supervisor representing a district that includes Del Mar, Solana Beach and Encinitas, and extends inland to cover the city of San Diego's northern neighborhoods and Escondido.