As it turned out, no relatives of the victims - 34-year-old Keisha Williams and children Keiearra Williams, 15; Thomas Reed, 10; and Terrence Moore, 7 - were present.
Assistant District Attorney Brendan O'Malley said afterward that he had told the victims' family to stay away because he knew Rosa would waive a preliminary hearing on four counts of second-degree murder and carjacking and assault charges.
"I told them, 'This is going to be a long, painful process,' " O'Malley said.
After the hearing, Warren said Rosa has been overcome with remorse about the four deaths. Warren said he hoped to negotiate some type of plea bargain with the prosecution.
Second-degree murder - a killing during commission of another felony - carries a mandatory sentence of life without parole.
Warren said Rosa and his mother had surrendered to police and were the first to identify Cornelius Crawford as Rosa's alleged accomplice.
"Anything less than second-degree murder would be a gift in this case and frankly, that's what I'm looking for," Warren said.
O'Malley, however, said it was too early to talk about a plea deal for Rosa.
"I'm not sure we even need his cooperation," O'Malley said.
Rosa's decision means his case will move to trial.
Warren said Rosa agreed with his advice not to force the owner of the carjacked SUV - who police say was sexually assaulted during the carjacking and seriously injured in the crash - to testify at a preliminary hearing.
"That would just be a continuation of the trauma she's been put through," Warren said. "I don't think that's in anyone's best interest."
The preliminary hearing for Crawford, 24, was postponed to Oct. 21. O'Malley said the hearing would be protracted and that he expected to call about a dozen witnesses.
"This was a tragic thing that happened," Crawford's defense lawyer, C.P. Mirarchi III, said afterward. "He had no intention to hurt those kids."
Mirarchi said he still needs to see the prosecution's evidence: "I still have to find out what happened. We could be disputing some facts."
Rosa's family was not in court Wednesday but Crawford's stepmother, sister, and aunt were.
"He isn't a monster," said Crawford's aunt, Vonda Bowser, who said he had been looking for work since being paroled in February after serving almost seven years of a six- to 15-year sentence on a 2007 armed-robbery conviction.
Police said two men carjacked a Toyota 4Runner, sexually assaulted its driver, and drove at high speeds to Allegheny and Germantown Avenues, where they lost control of the car. The family they hit had been selling fruit to raise money for a church.
Both defense lawyers said their clients were in protective custody and on suicide watch. Warren said he told Rosa about Keisha Williams' Aug. 7 death in the hospital 20 minutes before Wednesday's court appearance.
"He buried his face in his hands," Warren said.