Bradley Dack's tenth goal of the season wasn't enough as Rovers were left frustrated for the second time in three days after some late heartbreak at the New York Stadium.
Dack confidently slotted home mid-way through the second half to hand Rovers a deserved lead in south Yorkshire.
But just as it looked like the points were heading back to Ewood Park, David Ball scored from close range in the final minute to scramble a point for Rotherham at the death.
Tony Mowbray made three changes to the side who picked up a point at home to Scunthorpe just two days earlier for the clash with the Millers.
Two were enforced, with Paul Caddis and Craig Conway coming in for Ryan Nyambe, who was carrying a knock and only fit enough for the bench, and Marcus Antonsson, who picked up an ankle injury in the draw against the Iron just a couple of days earlier.
Conway's return from illness was timely for that exact reason, after the Scot missed out on the game against the Iron last time out. However, Joe Nuttall was still yet to fully recover from a virus.
Also coming into the side was Corry Evans, who replaced Peter Whittingham - the ex-Cardiff man dropping to the bench.
With a couple of senior players missing out, Mowbray handed young striker Dan Butterworth a place on the bench.
Hosts Rotherham made one change, with captain Richard Wood returning to the starting XI and replacing Lee Frecklington, who missed out through injury.
In a lively start from both sides, it was the hosts who had the best early opportunity, with David Raya doing well to dive low to his right to turn behind Will Vaulks' bouncing effort with just ten minutes gone.
Rovers started finding their mojo going forward and could have scored a couple of times mid-way through the half with Derrick Williams, Danny Graham and Elliott Bennett all seeing attempts saved by Marek Rodak or blocked in a goalmouth scramble.
Just moments later and a strong run from Josh Emmanuel from the hosts resulted in the Ipswich loanee's cross finding David Ball at the near post, but the striker headed comfortably wide of Raya's goal.
Williams was next to try his luck from range but saw Rodak bat his effort over the upright on the half hour mark.
Eight minutes before the break and Ball came so close to finding the top corner with a curling effort but his attempt whistled past the post.
Rovers upped the gears after half time and the returning Caddis fired into the 1,821 visiting supporters behind the goal after being set up by ex-Millers man Richie Smallwood.
A Rotherham double change was mirrored by Mowbray just after the hour with Nyambe and Dominic Samuel entering the action in place of Caddis and Conway as Rovers altered formation and went with two up front.
And just moments later the changes paid dividends as Samuel played his part before Smallwood found Dack racing through and the number 23 celebrated turning 24 by burying beyond Rodak and handing Rovers the lead.
The visitors were having to withstand some fairly strong Rotherham pressure as the hosts looked to grab a quickfire equaliser, but still looked dangerous on the counter with the added pace of Samuel.
With time running out Mowbray looked to hold on to the lead by bringing on Elliott Ward for Graham with five minutes to go.
But Rotherham's pressure was increasing and eventually Paul Warne's side found a way through as a corner was flicked on at the near post and the lurking Ball prodded home from close range.
Rovers were thankful to Raya for grabbing the ball after substitute Jonson Clarke-Harris beat his man and went goalwards but that was to be the final action of the clash and it ended all square.
It was a bitter pill to swallow for Rovers, who had shaded the game throughout, but couldn't find a decisive second goal.
Rotherham: Rodak, Emmanuel, Mattock, Vaulks, Ajayi, Wood (c) (Ihiekwe, 83), Forde, Ball, Towell, Yates (Clarke-Harris, 59), Williams (Newell, 59).
Unused substitutes: O'Donnell, Purington, Cummings, Wiles.
Goal: Ball, 89
Rovers: Raya, Caddis (Nyambe, 64), Downing, Mulgrew (c), Williams, Smallwood, Evans, Bennett, Dack, Conway (Samuel, 64), Graham (Ward, 85).
Unused substitutes: Leutwiler, Whittingham, Tomlinson, Butterworth.
Booked: Mulgrew, 77
Goal: Dack, 66
Attendance: 9,247 (1,821 away)