The VLA parameters generated using this command are apparently are no longer used as of 2007 or earlier. The capability to specify the parameter has been left in place, but should not be used.
Description for historical interest:
VLAROT gives the name of the VLA ROT file that contains such things as control information for subreflector focus and rotation, collimation errors and control parameters for each frontend.
Note that, if any of FLUKEA, FLUKEB, VLAFEAB, VLAFECD, VLASYNA, VLASYNB, VLAIF, FEFILTER, or VLAROT are specified, both LO and FI cards will be made. In such cases, any other parameters allowed to default will be set to the standard value for the specified VLABAND.