The duo dominated the event, which was held for the first time in Bangkok's Rajamangala Stadium, winning every head-to-head tie in which they competed.
In the final, Schumacher defeated Formula 1 rival Romain Grosjean in the first heat after the Lotus driver lost a lot of time with a lurid slide at the last corner in the KTM X-Bow.
Vettel then defeated World Rally Championship ace Sebastien Ogier in the second race to clinch the Nations' Cup title.
Speaking after the victory, Schumacher vowed to return in 2013 in search of a record-extending seventh crown.
"For sure, we're going to be here, that's a must," said Schumacher. "Actually, my lucky number is seven so we are going to push hard!"
Team Australia, represented by four-time Australian V8 Supercar champion Jamie Whincup and five-time 500cc motorcycle champion Mick Doohan, had a strong run to the semi-finals before being knocked out by Germany.
But Team Germany did have its only major scare of the evening against Australia, with Vettel understeering into the barrier driving the 570bhp Lamborghini Gallardo Super Trofeo before recovering to win.
In the other semi-final, Team France defeated the All Star team of Le Mans legend Tom Kristensen and two-time MotoGP champion Jorge Lorenzo.
In the group stages that preceded the semi finals, France and the All Stars qualified from a group that also contained the Americas and British teams.
Team Americas, represented by IndyCar champion Ryan Hunter-Reay and Production World Rally champion Benito Guerra, only missed out on a semi-final slot on a best time tie-breaker after matching the All Stars team's three group stage victories.
British pairing David Coulthard and Andy Priaulx only won twice, with both drivers losing wins to penalties for touching the barriers.
In the other group, the ROC Asia-winning Team India finished third with two wins for Karun Chandhok and Narain Karthikeyan, with both drivers struggling after having no prior opportunity to learn the track's chicane, which had been revised overnight.
Team Thailand finished bottom of the table with one win shared by Charoensukawattana Nattavude and Tin Sintrai.
The Race of Champions itself, in which drivers compete individually, takes place on Sunday.