Roddick will begin play at the Family Circle Tennis Center against Vladimir Voltchkov.
"It will be exciting to get out there first and get out of the gates, but either way you've got to win three sets," Roddick said. "It's important to get off to a good start and that responsibility is on me right now. I'm looking forward to it."
Fish will then take on Max Mirnyi, the leading player from Belarus. They met at the Olympics last month with Fish winning en route to the silver medal.
Twins Bob and Mike Bryan will face Mirnyi and Alexander Skrypko in Saturday's doubles match. The reverse singles will be played Sunday.
The United States has not won the Davis Cup in nine years, but beat Austria and Sweden to reach the semifinals. Belarus has defeated Russia and Argentina in its Davis Cup World Group debut.
France will play in Spain in the other semifinal. The Davis Cup Finals will be held in early December.
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