In MAME listxml there's a field for each game like this:
<display tag="screen" type="raster" rotate="0" width="384" height="224" refresh="59.637405" pixclock="8000000" htotal="512" hbend="64" hbstart="448" vtotal="262" vbend="16" vbstart="240" />
I think the Info.Rotation data comes from this, but is there a way in AM to get also the width and height data from this tag? This is the "native" resolution of the machine and could be useful for CRT filters if your screenshots are not pixel perfect...