I know you said you already tried this, but this is what I have, and it works all the time.
I edited the scummvm.desktop file and changed the exec= line to point to a script.
The script is just:
#!/bin/sh
echo "Rot270" > /tmp/qtembedded-root/QtEmbedded-0.spec
scummvm -g normal
The only problem with Scummvm for me now is that it doesnt draw black bars on the top and bottom, so you can see opie along the edges. Games are perfectly playable though.
Edit: Ok, I just read your post a little closer and noticed you were changing /tmp/qtembedded-zaurus/QtEmbedded-0.spec.
It should be /tmp/qtembedded-root/QtEmbedded-0.spec that has the Rot270 line in it. I didnt need any of the other lines for my 5500 using the 3.5.1 Scummvm.