Launching mintstick from dmenu or rofi is not going to work because the application mintstick requires an option behind the command.
mintstick -m format
mintstick -m iso
That is the code it is waiting for.
If you use ALT + F3 you are using the menu of XFCE and behind the icon is the correct launch sequence.
That is how I launched Usb Image Writer.
But you can launch it from a terminal as well.