Johnson was delighted with his team's display in the wake of defeats against Derby, Walsall and Peterborough in their three previous matches.
Rooney regained the lead for Oldham in the 56th minute with a simple tap-in and James Dayton sealed victory with 14 minutes left with a super strike.
"It has been a horrible two weeks not winning, but we can now go round with a smile on our faces," Johnson said.
"I was proud of my lads in what was a must-win game. It was a good day and there were a lot of good performances.
"I think we deserved our win and to a man we performed well."
Johnson added he was pleased with the way his side stood up to the physical challenge of playing against the Valiants.
"We had talked about winners all week, and we were winners. We stood up well because Port Vale aren't easy to play against," he said.
"The game had a bit of everything. It was high-tempo, a lot of balls in the box and some good football was played at times. There were shots, chances and a penalty saved.
"I don't think you could ask for more - perhaps we must charge more."
Johnson said it is important his team builds on the victory.
"We need to keep doing the right things. The table is looking healthier after this victory so let's kick on," he added.