Welbeck completed an estimated £16 million switch to the Emirates Stadium on transfer deadline day after the arrivals of Radamel Falcao and Angel Di Maria further limited his first-team chances under Louis van Gaal.
He could be set for an extended run in Arsene Wenger's side when domestic football resumes next week, with Olivier Giroud sidelined for four months.
And, while Rooney accepts Welbeck had a difficult decision to make in leaving his boyhood club, the United and England skipper believes the 23-year-old has made a switch that will benefit all involved.
"Danny is a lively player, an impact player," Rooney said.
"He is quick, he can score goals and I am sure with him getting the move to Arsenal now, hopefully he can play up front for Arsenal. That will really help him with England.
"He is a Manchester lad and I spoke to him a few times.
"It was a really tough decision for him to move, but for his professional career, he felt he had to.
"Hopefully he can get a few games up front which would benefit him for England."
Welbeck will be hoping to take advantage of Daniel Sturridge's thigh injury to line up alongside Rooney in England's attack when they open their Euro 2016 qualification campaign in Switzerland on Monday.
