Roger-Vasselin broke the American twice in the final set to lead 5-1 before converting his first match point with a forehand winner.
Roger-Vasselin will next play either Paul-Henri Mathieu or Albert Montanes.
The Open de Nice is a warm-up tournament for the French Open, which starts Sunday.
Results from the fifth day of the ATP Nice Open tennis tournament (x denotes seeding):
Quarter-finals:
Albert Montanes (ESP) bt Paul-Henri Mathieu (FRA) 6-4, 6-1
Edouard Roger-Vasselin (FRA) bt Sam Querrey (USA x3) 3-6, 7-6 (7/2), 6-1