For starters try loading Gnomebaker as root and see if that fixes things. If so, we have established its permissions related.
I will update this post with further answers once i have Gnomebaker installed.
Update:
Right so I didn't notice one part of your error message: "No such file or directory". Basically its throwing this up because /tmp/GnomeBaker/root/ doesnt exist. Unfortunately this program is somewhat lacking in its ability to plan ahead. It sets this directory as its temporary work space but doesnt create the path in the filesystem.
If you
Code:
$ mkdir -p /tmp/GnomeBaker/root
or
$ mkdir -p /tmp/GnomeBaker/<username>
you will be able to do what you want.