Roadside assistance covers towing in case of puncture where the car can't be driven anymore.
If spare tyres are standard on your vehicle, you have to leave one in the car for the driver in case of flat tyre.
In case of puncture, tyres are on the driver. If it's necessary to change two tyres or more after a puncture, the driver will have to pay for the replacement of the tyre and 50% of the second tyre; the other half will be at your charge.
NB : If the puncture is due to an abnormal wear of the tyres, all expenses will be at your charge.