Albion revelled on their return to League One, thanks to their only permanent summer capture.
Alex Revell made a dream debut for the Seagulls with a superbly taken goal shortly before the break.
It was the perfect start for the prolific former Braintree marksman and for Mark McGhee's side after a difficult pre-season, which lowered expectations.
Dean Cox, who provided the pass for Revell's winner, was controversially sent off on his full debut two minutes later for a second bookable offence, having been cautioned in the first instance for going into the Albion fans to celebrate Revell's strike.
Albion, with Joel Lynch a commanding figure in the heart of the defence, coped comfortably with ten men in the second half.
Tony Stokes made a tidy debut in the centre of the park and there will be better to come from the West Ham youngster.
The first surprise of the new season was the Albion starting line-up. There were no places for Colin Kazim-Richards, Alex Frutos or Keith Lowe.
McGhee and his coaching staff have been frustrated by Kazim-Richards' preference for lying deep in search of trying something spectacular, rather than getting into the box to poach goals.
Frutos signed a new contract in the summer but the Frenchman was upstaged during pre-season by the diminutive Cox.
Lowe's omission was more about giving him time to bed in following his loan move from Wolves earlier this week.
Stokes arrived even later from West Ham but the teenage playmaker went straight into a three-man midfield with Richard Carpenter and Dean Hammond.
Adam El-Abd partnered Lynch in the centre of defence, Paul Reid and Kerry Mayo providing experience either side of them in the fullback positions.
Cox was given his full debut alongside an all-Essex front pairing of Gary Hart and Revell.
First year pro Cox made his only previous appearance as a substitute in the home game against Plymouth towards the start of last season.
Rotherham, favourites for the drop due to a ten-point deduction for slipping into administration and their narrow escape from relegation last year, paraded no fewer than six of their nine new signings.
The exceptions were Justin Cochrane - ruled out of the start of the campaign by a knee injury - Martin Woods and Scott Wiseman, who both occupied places on the bench.
With so many new players on show there was an opportunity for somebody to quickly make a name for themselves.
Blocked The chance to do just that fell to Revell inside the opening two minutes. Paul Hurst, the Rotherham leftback, made a mess of an attempted header back to his keeper Neil Cutler. Revell nipped in but his effort was blocked by the advancing Cutler.
The keeper deserved credit for reacting swiftly to Hurst's error but it had to go down as a gilt-edged opening for Revell to launch his career with the Seagulls in eye-catching fashion.
Albion spurned another glorious opportunity to break the deadlock later in the first half when Hammond ghosted in ahead of Cutler to meet a left-wing cross from Cox with an unchallenged header which went inches wide of the vacant net.
The Seagulls were quite content to soak up spurts of Rotherham pressure when they were not in possession by operating a 4-5-1 system, with Revell and Cox dropping in on the flanks to help the midfielders.
Route one almost worked for Albion when Wayne Henderson's long clearance was headed on by Revell for Hart to chase menacingly. It required a last-ditch tackle by the powerfully-built former Derby defender Pablo Mills to deny him.
Henderson, given the nod in goal over Michel Kuipers, was reasonably well protected by his back four in the first half, Lynch in particular catching the eye with his calmness.
Henderson was forced into serious action early on when the defence failed to deal with a long throw from Mills, the Republic of Ireland No. 3 reacting smartly to turn behind Richie Partridge's drive from an acute angle.
The first half exploded into life shortly before the break with a wonder goal by Revell and a bizarre red card shortly afterwards for Cox.
There did not seem that much danger to Rotherham in the 43rd minute when Cox fed Revell just inside the area but he made ample amends for his early miss with a right-foot curler beyond the diving Cutler just inside the far post.
Revell was booked for his celebration and Cox was also cautioned for over-exuberance in front of the Albion fans behind Cutler's goal.
That took on extra significance in final minute of the first half when Cox was shown a yellow card by referee Colin Webster for a foul midway inside his own half and then, straight afterwards, red.
Cox's mystified colleagues surrounded Webster to protest as Cox made the forlorn walk towards the dressing rooms.
With the departure of Cox, Revell's reward for his exquisite strike was to chase around alone up front as Hart withdrew to the right flank.
Kazim-Richards took over the sole striker role from the tiring Revell in the 57th minute but only after the goalscorer had nearly doubled Albion's lead, dragging a shot wide following an aerial error by Mills.
Rotherham lacked ideas and penetration and Albion's numerical disadvantage was barely noticed.
The home side offered little apart from a header by highly-rated midfielder Lee Williamson from a cross by Partridge which Henderson held as he moved to his right.
Young centre forward Dave Hibbert, drafted in on loan from Preston for six months, made no impression on the Seagulls' resolute rearguard.
Hibbert had already been penalised for handball when he blazed over just before he was taken off.
His replacement Woods, another of the Millers' newcomers signed from Sunderland, tried to emulate Revell's impact for Albion with a header which Henderson again dealt with competently.
Michael Keane shot wide after making space for himself and Partridge sliced another effort wide in Rotherham's unconvincing attempt to prise an equaliser.
Kazim-Richards almost increased Albion's advantage on the break when he escaped from Ian Sharps to fire into the side-netting.
Rotherham had to wait until the stroke of full-time for their best chance of the match, substitute Woods scooping over Partridge's cross from point-blank range.
That would have been rough on Albion. They deserved to take all three points, particularly for the way they performed once reduced to ten men.
Comments: Our rules
We want our comments to be a lively and valuable part of our community - a place where readers can debate and engage with the most important local issues. The ability to comment on our stories is a privilege, not a right, however, and that privilege may be withdrawn if it is abused or misused.
Please report any comments that break our rules.
Read the rules hereComments are closed on this article