Errani beat Anna Tatishvili of Georgia 6-2, 6-1 for her 14th successive win on clay, and Vesnina eliminated fifth-seeded Marina Erakovic of New Zealand 6-2, 6-4 in the other semifinal at Romai Tennis Academy.
"Anna played a good match, she played strong, but maybe she was a bit tired after the long match she had yesterday," Errani said.
Tatishvili took 2½ hours to beat Aleksandra Wozniak of Canada Thursday.
Errani reached her eighth career WTA final. She has won four finals.
The final will be the sixth for Vesnina, who has yet to win a title.