Police Scotland, which is treating the incident as attempted murder, said the teenager appeared to have been struck twice – firstly as the car was travelling forward on Stravannan Road, then again as it reversed.
Roisin’s sister, Jamieleigh, 21, who described her sibling as a “brave wee soul”, thanked the public for their support and urged anyone with information to contact police.
She said: “They drove away without even getting out to see if she was ok. It’s disgusting. They deserve to be caught. They should not be on the streets.”
Two girls aged 12 and 14 and two boys aged 12 and 13 were treated for minor injuries.
Detective Chief Inspector Craig Willison said: “We believe the 21-year-old was the intended target. We haven’t confirmed his injuries exactly at this point, however we believe they are minor injuries.” He added that police planned to interview the man as part of their investigation.
The owner of the Astra, later found burnt out in nearby Carmunock, has also been identified, but police are still trying to trace them.
Amid speculation the incident was part of an ongoing gang feud in the area, Mr Willison said the force had no information to link it to a “bigger picture” at this stage, but was exploring “all avenues”.
Asked if the 21-year-old was known to police, he added: “The police know who he is, yes.”
He added: “I believe that the answer to all this lies with the children who were there at the time, other people in the area, and the wider community.”
Superintendent John McBride said the incident was “dreadful” and generated “a lot of community concern”.