Roddick, from the United States, started slowly but recovered for a 1-6, 6-3, 6-4 victory over No. 4-seeded Czech Tomas Berdych while Stepanek, another Czech, ran over third-seeded Frenchman Gael Monfils 6-2, 6-1 in his semifinal.
Roddick had his serve broken twice in the first set while Berdych raced out to an advantage but settled down and didn't suffer another break on the day. He broke Berdych's serve early in the second set and held on to even the match.
It wasn't until the ninth game of the third set that Roddick again solved Berdych's serve, allowing the American to serve out for the match.
Stepanek, who has lost one set this week, was on the court just 61 minutes in his dismantling of Monfils. He broke the French player's serve twice in each set and won 70 percent of the points on his own serve.
Stepanek will be looking to repeat as the Brisbane International champion in Sunday's title match, which has a first-place check of $63,800 at stake. Roddick has won five of the six times he's played Stepanek, although the two split a pair of meetings in 2009.
Copyright 2010 by United Press International.