Luton Town 1 Rochdale 1
The visitors had looked short of ideas as they trailed to Tom Craddock's penalty at the break.
But Hill brought on Joe Thompson and Adam Rundle and both players combined for the equaliser in the 56th minute as Rundle drilled low under Dean Brill to earn a vital point.
Luton threatened in just the fourth minute when Ian Henderson crossed low from the right into the path of the on-rushing Asa Hall, whose shot was blocked by Ciaran Toner.
Lee Thorpe was booked for a heavy challenge on Keith Keane a minute later before the hosts created another opening in the eighth minute when Craddock fed Henderson, who saw his 15-yard shot blocked by Tom Kennedy rather than playing in Chris Martin.
Thorpe produced a 12-yard header from a Simon Ramsden cross that was easily held by Dean Brill on a rare Rochdale attack in the tenth minute.
Luton continued their momentum with Kevin Gallen drilling a 25-yard volley just wide in the 23rd minute and Martin mis-controlling at the vital moment after being played in by David Livermore four minutes later.
Hall fired a low 20-yard left-footed effort straight at Frank Fielding in the 28th minute before the Hatters finally made the breakthrough four minutes later.
Nathan Stanton was adjudged to have pushed Martin in the area and Craddock stepped up to blast home his 12th of the season from the spot.
Rochdale boss Hill made his double substitution at the interval and the decision paid off in fine style in the 56th minute as Thompson crossed from the right for fellow substitute Rundle to brush aside Michael Spillane and fire home under Brill from six yards.
Two minutes later, the visitors should have gone ahead when a two-on-one break saw Rundle feed Adam Le Fondre, but Dale's top scorer wasted the opportunity by cutting inside and blazing over left-footed from 16 yards.
Hall arrowed a 22-yard effort over the bar for Luton in the 61st minute but Rundle again showed his menace for Rochdale five minutes later, crossing for Thorpe to turn and blast an effort over the top from eight yards.
Dale almost won it in the 89th minute when Thompson chested down to Le Fondre only for Brill to save the striker's close-range effort.