1) Try to calculate slashes after ':'.
Your code:
Quote
$scgi_host = "unix:////root/scgi.socket";
One, two, three, four.
My example below:
Quote
// $scgi_host = "unix:///tmp/rpc.socket";
One, two, three.
Questions?
2) In your system both rtorrent and web users have permissions for read/write from/to /root ? Really?