"Early on we were like, 'It's going to be rough,' but the way the wind was blowing you never know."
DeRosa's two-run homer -- Chicago's fourth of the game -- capped a six-run seventh inning as the Cubs rallied for a 10-9 victory Friday, their fifth consecutive win.
Henry Blanco hit a two-run homer in the seventh -- his first since 2006 -- and Jim Edmonds, who had earlier hit his first homer as a Cub, delivered a two-run double in the rally.
With the wind blowing out at 15 mph, there were seven home runs, and Jeff Baker hit a team-record four doubles for the Rockies.
Edmonds, who was struggling when he was released by the San Diego Padres, was batting .167 before going three for four Friday.
The Cubs were down 8-0 in the fourth inning and still trailed, 9-1, entering the bottom of the sixth before consecutive homers by Kosuke Fukudome and Edmonds against Rockies starter Aaron Cook got them going.