I saw ROBOT MONSTER in 3D at the 3D Festival in Hollywood in 2013, with stars Gregory Moffett and Claudia Barrett in person. The 3D was fine. There's a fun effect in the Main Titles with the comic books that make up the background appearing in layers. Later, when Ro-man shows the survivors scenes of devastation, the left eye and right eye show different images entirely, creating an unusual effect perhaps best described as "headache-inducing."
Wade Williams, current owner of ROBOT MONSTER, has been approached about releasing the film on home video in 3D, but reportedly is demanding way, way too much money to license it.
Incidentally, a truly awful short subject that was distributed with ROBOT MONSTER called "Stardust in Your Eyes" is available on the just-released 3D Blu-ray 3D RARITIES from Flicker Alley. In it, comedian Slick Slavin does bad celebrity impressions.