The Rockies had lost eight straight games through Wednesday to fall nine games off the pace in the National League's West Division, but finished off a previous series with a victory before winning two straight against the Cubs.
On Saturday, Carlos Gonzalez's lead-off home run in the ninth inning gave him the cycle and the Rockies a 6-5 win.
Gonzalez led off the bottom of the inning against Sean Marshall (6-3) and hit the first pitch he faced into the upper deck of right field.
Colorado was coming off Friday's 17-2 win which saw the club record 11 consecutive two-out hits in the eighth and score 12 runs in the frame.
Gonzalez singled in the first inning, tripled and scored in the third inning and doubled in the fifth while adding a sacrifice fly in the seventh before homering to win the game. It was the sixth cycle in team history.
Miguel Olivo clubbed a three-run home run in the win. Jason Hammel went 7 1/3 innings in the start and was charged with four runs on six hits with five strikeouts. Huston Street (2-2) got the win for throwing a perfect ninth.
The Rockies trail San Diego by seven games in the West and are 5 1/2 behind San Francisco in the league's early wild card chase.
De La Rosa, a 16-game winner last season, makes the second straight and sixth appearance of his career against the Cubs.
He's 2-0 with a glittering 0.64 earned run average in the five previous games, allowing 10 hits and a single run in 14 innings while walking 10 batters and striking out 21.
The 29-year-old opened the season with three wins in four April decisions before an injury shelved him for May and June. He returned July 9 against San Diego but was winless in four starts for the month, allowing 19 hits and 19 runs in 20 2/3 innings.
De La Rosa is 2-2 in five 2010 starts at Coors Field.
For the Cubs, right-hander Carlos Silva tries for a second win of the season over the Rockies.
The 31-year-old downed Colorado, 6-2, on May 18 with six innings of six-hit, two-run ball and four strikeouts.
That win improved Silva to 5-0 in a stretch that eventually got him to 8-0 before an initial loss to the Chicago White Sox on June 12.
Silva is just 2-4 in his last eight starts, though he did record win No. 10 with a 5-2 defeat of Houston on July 26 at Minute Maid Park.
He is 6-1 with a 3.97 earned run average in nine road starts this season.
Chicago swept a two-game set from the Rockies at Wrigley Field from May 17-18, but lost three of four games between the teams held at Coors Field last season.