what is the roe of QC inspector in eletrical engineeing

It is not merely inspect the final product, quality control is about stopping errors, not just picking them out.
There is a saying 'You can't inspect in quality...you have to build it in'
Inspection is really just a way of quantify whether you are doing a good job of quality control further up the line.
Every reject should be analysed to find out why it occured and action taken to stop it happening again.

'Oi..you don't do it again!'
Del

Now adays I think they are the ones who make sure the majority of products fail just after waranty expires and not just before.