I was thinking about a .v4r extension, that is, yes an extension to indicate that that file is a vvvv root.
It could also have a fancy circle grey icon (instad of the square one) so people can understand visually that it is a vvvv root patch.
This distinction between normal patches and roots could have some benefits maybe, what do you think about it?
If you think it is a good idea, please tell me if there some way I can contribute to code it. I did not found a place in the vvvv-sdk where it is defined the regedit entry definition (maybe cause I'm too lazy :)