Allen crashed in from 20 yards to break the deadlock in the second half at Adams Park before Peter Vincenti doubled the advantage with 15 minutes to go.
With Chesterfield only able to claim a draw earlier in the day, Dale's lead at the top is now two points, while Wycombe are just three points clear of the drop zone
Reece Styche was inches away from giving Wycombe the lead in the 10th minute but his effort came back off the post.
Rochdale almost took the lead when Vincenti met Matt Done's cross only to see his volley superbly tipped wide by Matt Ingram.
Allen's first time volley gave Rochdale the lead in the 52nd minute as Sam Wood's header found the midfielder on the edge of the area and he crashed it past Ingram.
And after Michael Rose hit the bar, Rochdale doubled their lead in the 75th minute when Vincenti swept home from three yards following a goalmouth scramble after Ingram had initially saved from Oliver Lancashire.