In a heavy bottomed stainless skillet, over medium heat, combine the butter, sugar, water and salt. As the butter melts, stir a few times with a wooden spoon or spatula to combine. Bring to a boil and then don't stir or touch the mixture again until it is caramel colored.
While the toffee is boiling, prepare a large baking sheet by lining it with parchment paper or a silpat mat. (Do not use waxed paper, it will melt.) Scatter the pecans across the prepared baking sheet.
Once the toffee is caramel colored, remove from the heat and add the vanilla. Stir to combine. Quickly pour the toffee over the pecans. Sprinkle with salt. Let cool completely.
When the toffee is cool, break into pieces and sprinkle on top of your Mason Dixie Sweet Rolls!