Basing on your example, this seems more a vector tool work.
If the original source is a vector, you can edit this with Inkscape. If the image is a bitmap, you can import and trace it (as in this example).
Now, you can edit the path, it's composed by nodes:
Select all the nodes and simplify the path by hitting Ctrl+L
With the node selected, convert the lines in segments by hitting the proper icon:
Change the width of the stroke and obtain the final image:
Too rough? You can simplify less or adjust the nodes manually before convert the curves in lines:
As alternative you can use the sketch effect (Path... Path effects... +):
You can play with the parameters (it's one of the live path effects):
And obtain another rough image: