The Millers have been drawn in Group H (Northern section): Bradford City, Mansfield, Rotherham, Newcastle United U21s.
The games start in September and the Millers will play 2 of the 3 group games at home.
The top 2 from the groups will go into the regionalised knock out stages, with no extra time until the final.. Straight to penalties.
Games can be watched on Sky Sports in the UK
Here’s every how every group looks in the first round of this year’s competition:
Group A (Northern section): Accrington Stanley, Stockport County, Tranmere Rovers, Everton U21s.
Group B (Northern section): Port Vale, Salford, Wrexham, Wolves U21s.
Group C (Northern section): Carlisle United, Morecambe, Wigan Athletic, Nottingham Forest U21s.
Group D (Northern section): Barrow, Bolton Wanderers, Fleetwood Town, Aston Villa U21s.
Group E (Northern section): Blackpool, Crewe, Harrogate Town, Liverpool U21s.
Group F (Northern section): Barnsley, Doncaster Rovers, Huddersfield Town, Manchester United U21s.
Group G (Northern section): Chesterfield, Grimsby, Lincoln City, Manchester City U21s.
Group H (Northern section): Bradford City, Mansfield, Rotherham, Newcastle United U21s.
Group A (Southern section): Birmingham City, Shrewsbury Town, Walsall, Fulham U21s.
Group B (Southern section): AFC Wimbledon, Crawley Town, Wycombe Wanderers, Brighton U21s.
Group C (Southern section): Bromley, Cambridge United, Charlton Athletic, Chelsea U21s.
Group D (Southern section): Gillingham, Peterborough United, Stevenage, Crystal Palace U21s.
Group E (Southern section): Colchester United, Leyton Orient, MK Dons, Arsenal U21s.
Group F (Southern section): Burton Albion, Northampton Town, Notts County, Leicester City U21s.
Group G (Southern section): Bristol Rovers, Exeter City, Swindon Town, Tottenham U21s.
Group H (Southern section): Cheltenham Town, Newport County, Reading, West Ham U21s.