Vega Gateway - how do I define dialout lines?

I purchased a Vega 60G and it is hooked up to 4 analog POTS lines. I configured it with FreePBX per the Wiki (with SIP registration), and it works great and sound quality is outstanding. Incoming calls come in with the appropriate line phone number, and inbound routing is working great. How do I make sure that the Vega is picking the phone lines I want for outbound calls? For example, I want incoming calls to use the incoming rollover scheme of 1, 2, 3, and 4, but I want outgoing calls to use lines 4, 3, 2, and leave 1 open for incoming calls. How do I specify this in the Vega configuration? I don’t see any documentation for this.