"We need to keep it going as long as we can," Strasburg said.
Now Washington will try to equal its season high with a fourth straight road win behind Roark (12-7, 2.80 ERA). The right-hander is 5-1 with a 2.17 ERA in his last eight starts and 5-1 with a 1.78 mark in his last eight on the road.
Roark allowed five hits over seven shutout innings Wednesday, but did not get a decision after the bullpen blew his lead in a 3-2 home win over Arizona. He joined Adam Wainwright, Felix Hernandez, Clayton Kershaw, Cole Hamels as the only pitchers with at least 10 starts of seven-plus innings and one or fewer runs allowed.
Roark gave up seven runs in four-plus innings in a 7-2 loss at Philadelphia on May 3, but pitched better against the Phillies on July 13, surrendering one run and four hits over seven in a 10-3 road win.
Washington seeks a ninth victory in 14 meetings with Philadelphia this season, while the last-place Phillies (58-72) are looking for a fourth win in five games following Sunday's 7-1 home victory over St. Louis.
Ben Revere, who is tied with Colorado's Justin Morneau for the NL batting lead, is hitting .372 over his last 17 games after going 2 for 3 Sunday.
The Phillies will likely need another big day at the plate to back A.J. Burnett (6-14, 4.42), who has posted a 6.41 ERA while matching a career high with six consecutive defeats. The right-hander gave up five runs, four walks and struck out nine in 7 2-3 innings in Tuesday's 5-2 loss at Seattle.
"I'm not making pitches when I need to make pitches," said Burnett, who has a MLB-high 76 walks.
This will be Burnett's fifth start of the season against the Nationals. He is 2-0 with a 1.98 ERA in two home starts against them compared to going 0-2 with a 10.57 ERA in two road matchups. He was ejected for arguing with home plate umpire Chris Guccione after allowing five runs in 1 2-3 innings in an 11-0 loss at Washington on Aug. 2.
Anthony Rendon is 5 for 12 with two home runs against Burnett in 2014, while Adam LaRoche is 4 for 9 with a homer and three doubles. Denard Span has gone 5 for 12 against Burnett this year, and is 20 for 54 (.370) versus the Phillies this season.
Philadelphia's Cody Asche is batting .375 with four doubles in the season series, though Ryan Howard is 5 for 48 (.104) with 21 strikeouts and Chase Utley is 8 for 49 (.163) against the Nationals.