What is the point of roasting salt?
The recipe calls for heating a "pan" on medium heat. Without knowing what type of pan this is, there is no way of knowing what reaction is going on there. Let me venture a guess, though.

I guess the pan is cast or mineral, seasoned, iron. The salt will react with some of the compounds from the bottom of the pan, making it "change its color".

Other types of pans will, most likely, do nothing. Non-stick, steel, aluminum don't react with salt.

As to the function of browning the salt, I can only guess that the flavor changes slightly from whatever you sautéed in the pan. You could pick up fish or meat or vegetable flavors.

As a side note, salt is used to clean cast or mineral iron skillets.