Full-time: Derby County 3 Rotherham United 0
Rotherham United's winless run stretched to 13 matches after a comprehensive Championship defeat at Derby County.
The Millers were 2-0 down at the break and fell further behind just after 63 minutes. They are now nine points adrift of safety at the bottom of the table.
Kenny Jackett's men couldn't offer enough resistance and had only one serious attempt on goal, a fierce close-range shot from Joe Newell just before the interval beaten away by Scott Carson,
The Rams didn't have to play particularly well for their win and could afford to see Lee Camp save a 67nd-minute penalty from Tom Ince after Ince had been nudged in the area by Joe Mattock.
Camp had also kept out an Ince spot-kick in the first half, but the Derby man fired in the rebound to give the home side a 15th-minute lead.
Darnell Fisher, enduring a particularly tough afternoon, had brought down Ince.
Darren Bent added a Derby second four minutes later with a clinical cross-goal finish from the right.
Ince slotted in his second goal of the match in the second half as Bradley Johnson's header sent him running clear on a day which offered little hope for Rotherham in their survival fight
Jackett had changed formation and personnel after the home reverse against Preston North End a fortnight ago, switching from 4-4-2 to 4-2-3-1.
Greg Halford was selected at centre-half, Tom Adeyemi and Jake Forster-Caskey were paired together as defensive midfielders and Peter Odemwingie came in on the left, with Newell moving to a central role.
Striker Dexter Blackstock missed out completely and is thought to have picked up an injury, while there was a place on the bench for young forward Jerry Yates after his recovery from a groin complaint.
After a decent opening spell, the Millers were second best and are now without a victory since August 20.
Derby (4-3-3): Carson; Baird, Keogh, Pearce, Lowe; Johnson (Bryson 82), Butterfield, Hughes; Ince, Russell (Weimann 61), Bent (Vydra 69): Subs not used: Mitchell, Bryson, Shackell, Anya, Hanson.
Rotherham (4-2-3-1): Camp; Fisher, Halford, Wood, Mattock; Adeyemi, Forster-Caskey (Vaulks 61); Taylor (Brown 61), Newell, Odemwingie; Ward. Subs not used: Price, Kelly, Fry, Belaid, Yates.
Goals: Ince 15, 63, Bent 19 (Derby).
Referee: Oliver Langford (West Midlands).