De La Rosa (2-1) also notched the win, allowing four runs on seven hits over five innings.
Colorado got the victory after receiving news earlier in the day that team President Keli McGregor, 48, was found dead in a Salt Lake City hotel room Tuesday morning.
The Denver Post reported that Salt Lake police officials indicated McGregor had died of natural causes. His death will be investigated by the Salt Lake City medical examiner's office, police said.
De La Rosa's three-run double came after Todd Helton, Brad Hawpe and Melvin Mora had each knocked RBI singles in Colorado's explosive third inning.
The Nationals were led by Ryan Zimmerman's two-run homer while Cristian Guzman chipped in with four hits and an RBI in the defeat.
Scott Olsen (0-1) was saddled with the loss, allowing six runs on seven hits in just two-plus innings of work.