After the game finished 2-2 following the regulation 90 minutes and a period of extra time, a missed spot-kick from Orient's Chris Dagnall at Wembley Stadium ensured Rotherham won the final 4-3 on penalties at Wembley Stadium.
The dramatic shoot-out win for Steve Evans' Millers means the South Yorkshire outfit will play in the Championship in the 2014/2015 campaign and Orient will stay in City's division for the new season.
It also means that Phil Parkinson's squad now know twenty-two of the twenty-three opponents who will make up their league calendar.
The winner of Monday's (26 May 2014) League 2 Play-Off Final featuring Burton Albion and Fleetwood Town will find themselves on the Bantams' fixture schedule for the new campaign and will also complete the League 1 line up.
City's fixture list for their 2014/2015 Sky Bet League 1 campaign will be confirmed to supporters on Wednesday 18 June 2014 at 9:00am.
The 2014/2015 Football League season will kick off on Saturday 9 August 2014 and conclude on Saturday 2 May 2015.
City's confirmed League 1 2014/2015 opponents so far are:
BARNSLEY
BRISTOL CITY
CHESTERFIELD
COLCHESTER UNITED
COVENTRY CITY
CRAWLEY TOWN
CREWE ALEXANDRA
DONCASTER ROVERS
GILLINGHAM
LEYTON ORIENT
MILTON KEYNES DONS
NOTTS COUNTY
OLDHAM ATHLETIC
BRISTOL CITY
CHESTERFIELD
COLCHESTER UNITED
COVENTRY CITY
CRAWLEY TOWN
CREWE ALEXANDRA
DONCASTER ROVERS
GILLINGHAM
LEYTON ORIENT
MILTON KEYNES DONS
NOTTS COUNTY
OLDHAM ATHLETIC
PETERBOROUGH UNITED
PORT VALE
PORT VALE
PRESTON NORTH END
ROCHDALE
SCUNTHORPE UNITED
SHEFFIELD UNITED
SWINDON TOWN
WALSALL
YEOVIL TOWN
ROCHDALE
SCUNTHORPE UNITED
SHEFFIELD UNITED
SWINDON TOWN
WALSALL
YEOVIL TOWN