Johnson said: "Having been pegged back at 1-1, I told the lads they needed to go out and show a bit of character in the second half, as they had been on top.
"They did just that, and in the end it was comfortable. 52 points is usually safety, so we probably need three or four more wins."
The Robins boss has also called on his club’s supporters to turn out for Saturday's home clash with Nottingham Forest in great numbers, with a crowd of over 15,000 expected.