The Yorkshire club, aiming to join the elite with their eighth promotion in 12 years, made the most of home advantage to scrape what may be a crucial eight-point difference at a packed Clifton Lane. Fortunes swung dramatically in the last 11 minutes as Rotherham scored 10 points to turn an 11-9 deficit into a 19-11 victory and set up a tense second leg at Goldington Road on Sunday.
Rotherham played below par for much of the night, despite going into the game on the back of 17 consecutive wins. They were, however, urged on by their excellent forwards Mike Schmid and Neil Spence who demonstrated remarkable resolve to battle away until Bedford eventually cracked.
In the opening exchanges, the Yorkshiremen struggled to win line-outs and Tony Yapp, the Bedford stand-off, used the blustery wind to continually pin them back. Rotherham also suffered the loss of their stand-off Doug Trivella and their centre Jon Harper in the first quarter.
However, the replacement stand-off, Jake Niarchos, proved to be Rotherham's match-winner with an immaculate display of goalkicking. He landed his side's only points before the break with a 27th-minute penalty after Bedford were caught offside at a line-out.
That score was in response to the only try of the half, scored by the Scotland lock Scott Murray, who was forced over the line after Dan Zaltman's line-out catch. Yapp missed the conversion and was also wide with a penalty attempt as Bedford led 5-3 at the break and he was off target again before twice finding the mark as fortunes see-sawed. While Yapp struggled in the swirling wind, Rotherham drew confidence from the immaculate kicking of Niarchos, who landed all four penalty attempts as well as the conversion of his side's only try.
The turning point came on 69 minutes when Greg Austin's long cut-out pass was taken by the full-back, Mike Umaga, who scythed through Bedford's defence to delight the crowd.
Rotherham: Tries Umaga; Conversion Niarchos; Penalties Niarchos 4. Bedford: Tries Forster; Penalties Yapp 2.
Rotherham: Umaga; Lax, Austin, Harper, Walker; Trivella, Scully; Pinder, Garnett, Bunting, Webster, Kenworthy, Wade, Spence, Schmid. Replacements: Toews, Dudley, Cooke, Hall, Niarchos, Pattinson, Shepherd.
Bedford: Stewart; Whetstone, Murdoch, Harris, O'Mahony; Yapp, Crabb; Olver, Richards, Boyd, Zaltman, Murray, Cockle, Forster, Winters. Replacements: Davis, Underwood, Harrison, Duke, Howard, Odzemir, Elphick.
Referee: S Lander (Liverpool).