Clone the rollbar-agent repo:
$ git clone https://github.com/rollbar/rollbar-agent.git
Copy over the rollbar-agent files into your existing ratchet-agent directory.
Uninstall the ratchet-agent init.d service if installed:
service ratchet-agent stop
chkconfig --del ratchet-agent
rm /etc/init.d/ratchet-agent
Backup rollbar-agent.conf and rename your existing ratchet-agent.conf to be rollbar-agent.conf. Note that Rollbar libraries now write to .rollbar files rather than .ratchet files, so make sure you modify ext_safelist to include rollbar files and targets to point to the right files.
Install the new init.d script if desired:
ln -s /path/to/rollbar-agent/rollbar-agent-init.sh /etc/init.d/rollbar-agent
chkconfig --add rollbar-agent
chkconfig on rollbar-agent
service rollbar-agent start
If installing the init.d script, copy your environment specific configuration from your existing ratchet-agent-init.sh into rollbar-agent-init.sh.