The following screen shots show an example of working config on Tomato. In this example 192.168.4.1 is the local router 'gateway'
The OpenVPN config files can be found here
Router is linksys E4200 running Tomato
WAN: 192.168.5.0/24 by DHCP
LAN: 192.168.4.0/24 (router as dhcp server)
This is where you add the ca certificate
* Basic WAN set-up: specify DNS manually to avoid dns leak
* DHCP options: dns (need 3 for those devices that need 3 - against dns leak) + additional gateway setting required for my wifi clients only (possibly a bug ?)
* fix on syntax of mtu for openvpn