Earlier, Stan Wawrinka defeated Jo-Wilfried Tsonga, 6-1, 3-6, 6-3, 6-2.
A record 27,432 spectators watched the Davis Cup final in Lille's Pierre Mauroy stadium.
“If didn't want attention I would have been a librarian, so I think it's all good,” said the 20-year-old.
An all-star event will be held.
The Swiss No. 1 will be ready to play Gael Monfils on Friday despite doubt over back injury.
There's a lot more to the Davis Cup final than just Roger's missing title.
It wasn't easy, but Federer and Djokovic set up the final everyone expected.
Previewing a wildly unpredictable Davis Cup final between France and Switzerland.
The 1974 final may have been the most disappointing, but significant, in Davis Cup history.