It seems like rough edges happen sometimes  by accident. I want to make them on purpose and easily :)

Credit for this cake goes to The Pastry Studio

AYou could try rolling out and using the ball tool as usual, then pull on the thinned edge between finger and thumb in some places.

Thanks for the idea, Dayti!  I will try that...  So funny how it's a challenge to  make a fondant edge look rough and jagged on PURPOSE!  :)