You don't say what the roof is made of, but expect at least 60 years from a decent one. Many roofs have about around more than 200.
Slates, clay tiles last a really long time.
Concrete tiles have been around probably 70 years and don't wear out as such - just get wash out in appearance.
The biggest issue is probably loose nails / cracks in tiles cause by thermal stress. Use a pair of binoculars to look over it carefully from the outside. Then go up in the roof and look at it - check for felting in good condition (old roofs didn't have this).
Pay particular attention to places where mortar is used to secure tiles (ridge tiles, at eaves - these sorts of places).
Just because the neighbours have both changed the roof doesn't mean your house is a problem - they were probably 'sold' a roof by someone knocking on the door.
There is no safety reason why an electric radiator can't be used in a bathroom. Often it is done like this to allow a towel to be dried out in there during the summer (when the rest of the heat is off).
Probably not cost-effective to change it.