Sorry for not answering the last replies. I read them, but i was not convinced of the control scheme anymore, either. Other things than game programming had a higher priority at that time, too.
But i still like the idea of a platform game in combination with physics and rolling, so i thew together a new attempt this weekend* (and was surprised how much i learned about Unity in the meantime). But i have problems to motivate myself to work continuously on the same project... someday i'll finish this!
If i think too much about the same project, it's like it's already done and the programming work is just writing it down without many surprises (except annoying bugs and bug-hunting which is no fun).
*
http://forums.tigsource.com/index.php?topic=50053.0