His father, grandparents and about five of his friends watched from the public gallery.
The youth was granted bail on those charges, but police upgraded the charge to murder before he left the courthouse with his family.
Police said the murder charge followed provisional results of a post mortem examination that indicated Mr Rosillo died from stab wounds.
Community Magistrate Philip Greenbank declined an application for interim name suppression by the teenager's lawyer, Barry Hart.
But when Mr Hart indicated he would lodge an appeal an order was made banning publication of the name until 4pm on Friday, which is the deadline for an appeal to be filed.
The court was cleared of members of the public while legal argument was heard about whether he could be released on bail.
Bail on the assault and possession charges was eventually granted but with conditions.
He was ordered to live with his parents at their east Auckland address, be under a 24-hour curfew and be banned from using phones or contacting witnesses.
The teenager's father stood behind a fence at the rear of the courthouse waiting for his son to emerge.
Mr Rosillo and the accused were at a party in Greenhill Cres, Pakuranga, when the assault happened on Friday night.
Mr Rosillo died at the scene despite frantic attempts by his friends to keep him alive.
Detective Senior Sergeant Dave Glossop had said earlier that Mr Rosillo was stabbed after an argument about a girl.
He said police inquiries were continuing and they were yet to interview all the people who were at the party.
"There's a lot of traumatised teenagers as a result of this. His [Mr Rosillo's] family are also obviously devastated," he said.
- additional reporting NZPA
