I confirmed that it does not need to be placed into a Host block, as long as it is above all of your blocks.

For instance:

   UseRoaming no

   Host *
      Blah yes

Test with: ssh -v remote.ssh.host.com uptime 2>&1 | grep -i roaming

If it returns nothing, the config fix is active. If it isn't active, you'll see 'debug1: Roaming not allowed by server'