That's just for detecting if a game is vertical or not.
You should start by posting a log then it will be easy to see if the problem is on MAME or RL, but if rotate left/right are working I don't see why the rotate command wouldn't be sent as well since they are all in the same code section.
Umm looking at it I see the current MAME docs are a bit confusing so -rotate might actually work the other way around. This contradicts the info here though:
http://easyemu.mameworld.info/mameguide/options/31.html
Try editing the module and replace:
verticalRotationMode := " -rotate"
with:
verticalRotationMode := " -norotate"
and see if it works properly that way.