Judge Alan Mitchell fined her at Dublin District Court.
Rooney, with an address at Hedigan's B&B, Clontarf, pleaded guilty to stealing assorted products at SuperValu, Howth Road, Killester on October 17.
The prosecuting garda said the accused had the baby with her at the time and "some of the items were taken for the baby". The property was returned to the shop.
Rooney had stolen "baby items and general groceries", her solicitor, Caroline Egan, said.
The accused had had her baby nine months earlier and suffered post-natal depression as well as OCD.
She had been waiting for council accommodation for a number of years and had just got a flat in the south inner city, which would make a "huge difference" to her life.