Pompey struggled for fluency in a goalless first half at Fratton Park but they got into their groove after the break to run out 4-0 winners.
And three of their goals came from crosses – after Cowley highlighted Rovers’ problems in dealing with deliveries into the box and selected his team accordingly.
“It’s a really good win,” said Cowley. “We had to fight hard in the first half, when we were a bit too risk averse.
“But we managed to find a bit of rhythm towards the break and our message to the players was then just to free themselves up a little bit.
“We wanted them to be more courageous on the ball because we picked an attacking and technical team.
“That’s what happened and you saw more of a flow to our performance, particularly when we scored the second goal. You could see a confidence that perhaps hasn’t been there.
“We knew that Doncaster conceded a lot of goals from crosses, and so we wanted two of our best people at that if we got into those advanced areas.
“Marcus [Harness] and Reeco [Hackett] certainly have quality with their deliveries and I think three of our four goals came from balls into the box – either from open play or set-pieces.
“It's been a good week and after a good performance against the odds at Oxford and then digging in to beat Burton in midweek.
“In this game I thought the second half was the best we’ve played for a long time and it gave us a platform to build on.
“Things are coming together for us, but we’re still a work in progress and have to continue working hard.”
Pompey had lost four and drawn two of their previous six games in the league prior to beating Burton Albion last Tuesday.