One of the best explanations of the role and function of Government was given by Ezra Taft Benson. He titled his essay or talk (I'm not sure which it is), "The Proper Role of Government." I am not sure of the date this was written or in what forum it was given. I will provide more background as I learn it.
However, I heartily recommend reading it all the way through!!!!!!!!
It is available here on my blog and here as a pdf.