http://www.mameworld.net/pc2jamma/vantage2.html
NOTE:
   RUNNING GAMES WITH -rol,-ror or -origrotate RECREATES THE AUTHENTIC
   DISPLAY OF THE ORGINAL ARCADE GAME.
   ALL GAMES WITHIN VAntAGE RAN ON ROTATED MONITORS.
   HOWEVER, IT IS VERY IMPORTANT THAT YOU *NEVER* ROTATE A MONITOR
   THAT WAS NOT SPECIFICALLY DESIGNED FOR THAT PURPOSE.
Arcade monitors were obviously used in the games emulated by Vantage, so they are designed to be rotated with no problem.
I suppose most TV's and PC monitors are not specifically designed to be rotated, but they should be fine too.  A little common sense should work here - as long as you can safely/securely mount the screen all should be fine.