The substitutes combined in the 90th minute to earn the Robins their second win of the season, Hayles setting up Alsop for the only goal of the game.
"It was a good squad performance," said Allen. "We defended stoutly, defended resolutely and competed for everything. We played some good stuff against a decent team that has been in the play-offs for the last two seasons.
"To come up here and win keeping a clean sheet is very good for the club.
"I've said before that Julian helps us defend set plays and Rochdale were piling into our box asking questions. He went on and did that job and when the ball went up front he battled hard to keep it up there.
"He wasn't going to get in behind them because he is so slow but when Barry rolled that ball across the area he showed a tremendous change of speed - he actually got slower I thought - before knocking it into the corner."