The 37-year-old striker, who had not trained all week because he was on jury service, made an instant impression as the Robins overturned a goal deficit to land all three points.
"Barry's been on jury service all week so we haven't seen him, but when he came on he lifted everyone," said Cheltenham boss Allen.
"He's got that self-belief to hold on to the ball and definitely
got that hunger, which we see in training where he appeals for
every decision and still trains like a 17-year-old."
Allen also singled out Elvis Hammond for special praise but admitted he must address his side's slow start to the contest.
He added: "Elvis was magic. He was sharp as a razor and on another day could have had four or five goals - he looks a massive threat.
"It was a poor start though, the first 30 minutes we were poor.
Some of the new players I think it's fair to say froze, they looked leggy, slow and uncompetitive and didn't pass it either but in the second half they were absolutely superb."