I am thinking of replacing our cement board roof with the corrugated , painted / insulated steel roof panels . I am curious to know if there are increased risks from a lightening strike or does the foam backed insulation  mitigate that ? 

I bloody well hope not, I've just built a chicken broiler house with a 2000m2 roof of steel sheet!

 

But really, no, it isn't a problem, look at all the factories around with steel roofs.

Pre-coated composite roof sheets have been around for years no problem. ?

If you are concerned you can simply erect a steel crucifix on the peak of the roof, the locals will think its hilarious.

seriously though, lightning tends to strike the highest conductable source, so if your neighbours house is higher or even if there are high trees surrounding you or the electric pylon then its going there first.

 

You can of course make your crucifix into a lightning conductor but make sure you complete it with copper tails running down to the ground.

 

remember the advice about golfers, get rid of your club if on open ground and don't hide under a tree.

 

I think though, lightning striking a  steel roof will have no effect.

To get to earth it simply transfers to the steel roof, through the reinforcement in the columns and down to earth.

 

a timber roof though is a different matter.