Roadside assistance covers towing in case of puncture where the car can't be driven anymore.
If the owner left a spare tyre in the car, change it and let the owner know as soon as possible.
In case of puncture, tyres are on the driver. If it's necessary to change two tyres or more after a puncture, you will have to pay for the replacement of the first tyre and 50% of the second tyre; the other half will be on the owner.
If the puncture is due to an abnormal wear of the tyres, all expenses will be on the owner.