It is really easy to use tcp. Just load the right module and use @@host instead of @host.

I had to implement rsyslog for a customer, and we found out that many logs were losts when using only udp, even with tcp some are lost if you don't use spool queues on the sending host.

 I don't have the exact syntax to give examples here (you don't do this every day right?) but it is really easy to find howtos on the rsyslog website.