Create a full frame size rectangle.

• Tools -> Roto -> Full rectangle

• A Roto node with a full frame size rectangle is created.

• Copy 'fullRectangle' folder in your .Natron folder.
• Add following lines to your 'initGui.py' file, where <path> is the location of 'fullRectangle' folder.

from <path>.fullRectangle.fullRectangle import *
NatronGui.natron.addMenuCommand('Tools/Roto/Full rectangle','fullRectangle()')