Leeds looked dead and buried at half-time, trailing 18-6, but three tries in seven minutes at the start of the second half from Ryan Hall, Danny McGuire and Carl Ablett put the Rhinos in the driving seat as they put their defeat to Wakefield behind them.
Rovers will see this as an opportunity lost after giving the champions a run for their money.
McGuire also crossed for the Rhinos in the first half and Sinfield added four goals to his match-winning drop-goal.
Graeme Horne, Josh Hodgson, Michael Dobson, and Louis Sheriff scored The Robins' four-pointers.
Battling Bradford gave warning that they have not given up on a top eight place in the Stobart Super League with a 38-26 victory over struggling Widnes.
The cash-strapped Bulls recently suffered a triple blow to their play-off hopes through back-to-back defeats against Leeds and Warrington either side of a six-point deduction by the Rugby Football League for entering administration.
Michael Platt and Shaun Ainscough scored a brace of tries apiece for the Bulls, Brett Kearney, Ben Jeffries and Heath L'Estrange also going over.
Patrick Ah Van crossed twice himself for Widnes and Ben Davies, Danny Craven and Rhys Hanbury also went over.
Winger Jermaine McGillvary scored two tries to end Huddersfield's five-match losing run and secure Paul Anderson's first win as Giants coach with a 36-18 triumph over Catalan Dragons.
McGillvary's brace came in-between Remi Casty's score for Catalan Dragons before the hosts extended their lead to 24-6 at half-time thanks to tries from Scott Grix and Aaron Murphy.
David Fa'alogo and Lee Gilmour also touched down after the interval, while scrum-half Danny Brough converted all six tries to help Huddersfield forget their recent woes before Daryl Millard and Damien Blanch scored late consolation tries.
Wakefield's strong finish to the Stobart Super League season continued with their second win over fierce rivals Castleford this season, as the Wildcats emerged 40-12 victors.
Wakefield went into the break with a 16-0 lead thanks to early tries from Ben Cockayne and Richie Mathers, with Australian scrum half Tim Smith then touching down on the half-hour mark.
Dean Collis, Danny Kirmond and Lee Smith extended the advantage 15 minutes into the second half, before Castleford finally got on the score sheet through Paul Jackson's try on 61 minutes.
Nick Youngquest added another consolation score 11 minutes later, but Mathers went over late on to cement a comprehensive victory for the Wildcats, their third successive league win.