The second match, between sixth-ranked James Blake and No. 12 Tomas Berdych, could be the key to the best-of-five series.
Roddick, ranked fourth in the world, will face Ivo Minar in the opening match, and even the clay surface should not stop the American from winning.
"It should be tough, but I feel like I'm ready," Roddick said.
If the Americans have the better players on paper, the Czechs are counting on the imponderables of the Davis Cup to squeeze into the quarterfinals.
The 7,500-capacity CEZ arena is a sellout throughout the weekend and will be all Czech. And the hosts have spread the floor with clay, by far the least favorite surface of the Americans. They have not won a Davis Cup World Group match on clay in a decade.
"Clay might be my biggest advantage. That and the home crowd," said Berdych, a hard-hitting 21-year old player who is 5-1 on clay in the Davis Cup. Blake is just 4-3 on the slow, red powder.
Doubles are set for Saturday with reverse singles on Sunday.
Usually, Bob and Mike Bryan are untouchable in doubles. And having won the Australian Open last month, they are as good as they get. It should turn into an automatic point for the Americans.
Yet this time, the Czechs have more than a haphazard jumble of two players thrown together.
Lukas Dlouhy teams up with his 36-year-old coach Pavel Vizner. Last year, they won two doubles titles on clay and reached the semifinals of the French Open on the same surface. They finished as the No. 10 doubles team.
"We really respect them. We will not take them lightly," said Bob Bryan, who is 4-0 on clay in the Davis Cup with his brother.
The United States lost to Russia on clay in Moscow in last year's semifinals, and Roddick was twice beaten, reports AP.
Minar wants to keep Roddick's slump going and feels his lack of fame will help.
"He's likely never seen me playing. It could a bit of an advantage for me. He's among world top players and I've got nothing to lose. But I'll have to fight," Minar said.
The Czechs already jeopardized their chances of an upset well ahead of the draw when their No. 2 player, Radek Stepanek, pulled out to concentrate on the ATP Tour instead.
The Americans are 4-1 against the Czechs in Davis Cup play.