The Robins climbed into second in the league after winning five of their six league games in the month, though they still trail table-topping Scunthorpe by four points.
"It is nice to get the manager of the month so late in the season because it means my team has accumulated a lot of points," said Johnson.
"Jamie McCombe's goal at Doncaster was probably the highlight of the month as it came so late in the game to enable us to win 1-0 and it could be important come the end of the season."
And with six games to play, Johnson is setting his sights on overhauling the Iron at the top of the table.
"It is in our hands and we can catch them, they will be looking over their shoulder at us," he insisted.
"We are trying to keep positive and look ahead and if we are to go up it would be nice to do it as champions."