Copper roll tops come in two forms. One with a metal ring that 'holds' the roll and one that is without any reinforcement.
There are two types of ring used for Copper Pans, Jam Pans, Mixing Bowls, Cul de Poules or Fish Kettles one made from bronze or brass and ones made from cast or wrought iron.
The main problem occurs with iron rings, they become rusty and break, sometimes catastrophically other times by 'bursting' and coming apart - be aware of old pans like this - they can look fine but as soon as the ring takes any sort of pressure you either have a floor covered in rust or a broken pan rapidly becoming an ornamental piece of copper.
The easiest way to find out if your iron ring is getting too old for the pan, is to use a sharp piece of metal and dig into the ring - if it is soft leave well alone if there is no 'give' you have a good old pan.
Another thing to look out for is excessive damage on the top of the roll, if it is flattened have a good look at the ring, cast iron is quite brittle and can break quite easily.
Because there is usually a gap between the roll and the edge, dirt and contamination can get into the roll. The easiest way of cleaning these is turning the pan upside down and using a brush and a good hot water supply, scrub for all you are worth. Then turn up the right way and let it dry thoroughly.
We at Normandy Kitchen check all our roll tops for completeness and any damage, our exacting standards mean you never get a bad pan, or a broken ring!