I have fairly similar lookking set. Different brand and might be done in a different place. I removed the handle without drama long time ago. As far as I remember I just removed the hex socket screw and pulled the hand wheel. The hand wheel has a key, it won't turn on the shaft.
When I go home today, I could go into garage and check how to take handwheel out of my rotab.
I definately bin all original keys and generally original screws, they are pretty appalling quality.
Pekka