A 48-year-old man was sentenced Friday to 45 years to life in prison for sexually assaulting three girls he lived with in Lake Forest and Laguna Hills. Just as his trial was about to start in January, Ruben Roman pleaded guilty to 15 felony child sexual assault charges. Roman has credit for 1,259 days in custody, nearly 3 1/2 years. Roman dated the mother of the girls and lived with them for about four years, according to testimony from sheriff’…