Roddick made 36 of 42 points on his service and never faced a break point against the Argentine.
"Luckily the court here is helping out a little," Roddick told the Mercury News. "I'm able to mix it up a little bit more. My first serve was 74 (percent) last night and 73 percent tonight. I'll take that."
Looking to rebound from his quarter-final defeat by Marin Cilic at the Australian Open where he was bothered by an injured shoulder, Roddick has yet to drop a set in San Jose.
Roddick is an impressive 30-5 all-time in San Jose where he feels right at home.
"I was comfortable out there tonight," he said. "I was able to kind of move the ball around a little bit more. That just comes with getting matches in."
In the next round he will take on Tomas Berdych from whom he has won four of six matches.
In other action, American Sam Querrey reached his second straight SAP Open quarter-finals with a 6-4 6-4 win over Taylor Dent.
"It feels good," Querrey told reporters. "I come to tournaments like this expecting to win. I'm working harder off the court. I've paid my dues, I've created this."
Unseeded American Michael Russell reached his first ATP quarter-final with a gritty victory against Xavier Malisse. Russell and Querrey will meet in the quarters
Meanwhile, Ricardas Berankis defeated Bjorn Phau 7-6 6-3 and second-seeded Fernando Verdasco overcame Benjamin Becker 7-5 6-2. (Writing by Jahmal Corner in Los Angeles; Editing by Alastair Himmer)