A quick way to reset the feather curves in Nuke's Roto node

resetRotoFeather.py

# Current frame on the timeline
frm = nuke.frame()

# Iterate over all Roto nodes
for rotoNode in nuke.allNodes('Roto'):
    # Access the curves knob, then the root layer
    curves = rotoNode['curves']
    rootLayer = curves.rootLayer

    for spline in rootLayer:
        spline = curves.toElement(spline.name)

        # Iterate over each point in the spline
        for pt in spline:

            # Reset the center feather to a zero offset
            pt.featherCenter.addPositionKey(frm, [0, 0])

            # Grab the current coordinates for the left and right tangents
            lt_pos = list(pt.leftTangent.evaluate(frm).position)
            rt_pos = list(pt.rightTangent.evaluate(frm).position)

            # Match the feather tangents to the main tangents. We just need x and y
            pt.featherLeftTangent.addPositionKey(frm, lt_pos[0:-1])
            pt.featherRightTangent.addPositionKey(frm, rt_pos[0:-1])

# Update the curves view so we see the changes in the Viewer
curves.changed()