Valerien Ismael's Blackburn are now level on points with 22nd-placed Portsmouth albeit having played two games more, while Watford hover outside the play-offs in eighth off the back of Wrexham's comeback win at Queens Park Rangers.
The game took place at a mostly empty Ewood Park, as Blackburn's supporters began a boycott of home fixtures in protest against owners Venky's.
Earlier in the week, Rovers told BBC Radio Lancashire that they urged supporters to "show unity" despite the strength of feeling against their position.
For the home fans that were in attendance, it was a difficult opening 26 minutes as Watford played on the front foot, and took the lead through Kayembe's left-footed strike as a result of their seventh corner kick.
Yet that lead did not last for long as Blackburn also prospered from a corner kick, this time as Todd Cantwell's swinging set-piece was met by the onrushing Miller, who finished past visiting keeper Egil Selvik.
There was a short break in play before half-time as Watford's Rocco Vata, who had a spell out earlier this season due to a hamstring injury, was forced off.
Blackburn came into the match off the back of losing to Swansea in midweek, a match where they were without 13 players, as Ismael gave first senior starts to midfielder Brandon Powell, forward Aodhan Doherty and defender Connor O'Riordan.
His side finished stronger than they started, with Ohashi's late effort coming narrowly close to giving them what would have been an enormous three points, but in the end the result did few favours for either side in their respective aims for the season.