Roberts, who has guided the Dodgers to back-to-back appearances in the World Series, said he was determined to finally deliver a championship to the franchise after a 30-year drought.
"When I was hired to lead this team three years ago, I said at the time that managing the Dodgers is truly the opportunity of a lifetime and I feel the exact same way today," Roberts said in a statement.
"We've worked hard to develop a team and culture that will put us in position to win the World Series every season, but we still have yet to achieve our ultimate goal and that is what drives me each day."
Roberts, 46, has compiled a 287-200 record since taking over before the 2016 season. The Dodgers have won three consecutive National League West titles but have fallen short in the World Series.
They were beaten in seven games by the Houston Astros in 2017 and then suffered a 4-1 drubbing by the Boston Red Sox this year.
Dodgers president of baseball operations Andrew Friedman said locking in Roberts was seen as crucial to the team's hopes of winning a World Series.
"Keeping 'Doc' as our leader on the field was a top priority this offseason," Friedman said.
"Now that we've accomplished that we are excited to collectively shift all of our focus to doing all we can to bring a World Championship to our passionate fans."