Somewhere I saw a ball mount (WD) that could be raised and lowered. It
had an electric motor on it to run the hitch head up and down. This would
allow you to tilt the trailer up and down to get thru those
whoop-de-doos.
Of course once thru the WDD you would want to run it back to level,
especially with 2-axle non-equalized rubber suspension.
Much cheaper than a fancy ball mount is caster wheels at the rear of the
trailer frame. As long as the rough spot is paved these casters will
support the tail of the trailer. Just go real slow - you don't want to
bang the tail of the trailer on the pavement or ground.
Al