Arsenal, who are three points behind United with two games in hand, will return to the summit if they beat Reading at the Madejski Stadium Monday.
United clinched a sixth straight home league win thanks to two goals in a minute from Ronaldo.
His first, after 34 minutes, was headed in from a Ryan Giggs cross, and he soon added another from a Carlos Tevez assist.
Rovers had David Dunn sent off for two bookable offences.
Chelsea lost ground at the top as they were denied a win by Tim Cahill's brilliant 89th-minute equaliser for Everton.
Avram Grant's side had had much the better of the game, and, had it not been for some brilliant goalkeeping from Tim Howard and two clearances off the line, they would have been comfortably ahead.
They seemed to have won it when Didier Drogba headed in Salomon Kalou's corner with 19 minutes remaining.
But with a minute remaining, James McFadden's shot bounced up off Juliano Belletti for Cahill to smash in an overhead kick.
Juande Ramos won his first league game as manager of Tottenham as they crushed Wigan 4-0.
Jermaine Jenas hit two, with the other goals coming from Aaron Lennon and Darren Bent.
The games between Portsmouth and Manchester City and Bolton and Middlesbrough both finished goalless.
In the day's early kick-off, Gabriel Agbonlahor hit an 85th-minute winner as Aston Villa came out on top in the second-city derby.
Birmingham captain Liam Ridgewell had given his former side the lead when he put through his own goal after nine minutes, before Mikael Forssell headed a 62nd-minute equaliser.
But with five minutes to go, Agbonlahor converted an Ashley Young cross to give Villa their first away win of the season. By Ben James, dpa