Blake, who lost to Youzhny in their only previous encounter in last year's semi-final, held off a spirited fightback by his opponent in a see-sawing contest that lasted three-and-a-half hours.
The American world number 13 failed to serve out the match when leading 5-4 in the fourth set, but held his nerve to clinch the tiebreak 7-3 when 19th-ranked Youzhny netted a forehand.
"For me to come through is a big moment for me and for the team."
US tennis player
"He played great and he's got a lot more experience than me in situations like this," Blake said in a courtside interview.
"For me to come through is a big moment for me and for the team. It's definitely my best performance. And playing at home makes it a lot more fun."
Blake's victory puts the United States on the brink of a record 32nd Davis Cup title with the dominant Bryan brothers, Bob and Mike, due to take on Nikolay Davydenko and Igor Andreev in Saturday's doubles tie.
The Bryans, winners of five grand slam titles together, have lost just one doubles match in 13 Davis Cup appearances.
Roddick starts with a win
In the opening match, the big-serving Roddick fired down 25 aces against Tursunov to wrap up victory in just under two hours and put the United States in early control.
"I felt pretty good out there," Roddick, 25, told a news conference.
"I've been serving pretty well in practice all week. I felt like I found my groove and that makes it a lot easier when the court is quick enough to take action on the serve."
Roddick, who regularly unleashed serves in excess of 140 kph on the slick, indoor surface, paid tribute to the crowd of just under 13,000.
"They were amazing and when they stood in that last game of the final set it was probably one of the coolest experiences of my career so far," said the American, who lost to Tursunov in five sets in last year's semi-final.
Russia, the defending champions who beat Argentina in last year's final in Moscow, have lost twice to the US in three Davis Cup ties.