Roujin Z is a 1991 anime movie with a screenplay by Katsuhiro Otomo of Akira fame.
The main draw of the movie is the incredible biomechanical design of the futuristic hospital bed for elderly people, which is the pretext for many bravura pieces of traditional animation.
Bluray :
The 2012 remastered Bluray is presented in fullscreen 16:9, cropped vertically.
In this screenshot, the left character's head is severely cut off :

Original Trailer :
Luckily the first DVD from Manga Video featured an original japanese trailer in 4:3 which reveals a noticeably bigger image.
We can actually see the left character's face : the composition is balanced, the image makes sense.

(the characters' proportions seem slightly stretched in height compared to the bluray)
Full frame :
When stretched back a little to make the lines match, the original trailer and the bluray assembled together have a global aspect ratio of 1.34:1 which is probably very close to the original format.

Conclusion :
Roujin Z is not a widescreen movie, its original aspect ratio is probably close to 1.34:1.