Prosecutors said the girl, known as Gigi by her family, died from asphyxiation from a combination of “pathophysiological stresses”.
Roughley had placed her face-down, tightly swaddled and strapped to a bean bag before covering her with a blanket.
The nursery deputy manager then ignored the cries and distress of Genevieve and showed “sporadic” and “fleeting” interest in her wellbeing for one hour and 37 minutes until she found her blue and unresponsive, prosecutors said.
Sentencing, Mrs Justice Ellenbogen told the defendant Genevieve’s death was “absolutely avoidable”.
She said: “As the harrowing CCTV audio and video footage showed, that day you left Genevieve in that position only carrying the most cursory and infrequent of checks.
“I am certain that every person in this courtroom who watched that footage was willing you to pick her up and remove her from the danger you had placed her, knowing of course that you didn’t.”
The judge went on: “It was apparent that at best you considered Genevieve to be a nuisance and at times displayed antipathy and frustration with her.
“Your interactions with Genevieve on 6 May and 9 May palpably lacked any care, kindness or concern for her wellbeing.”
As Genevieve’s crying “intensified” as she struggled on the bean bag, the judge told Roughley: “Even then you didn’t approach her, pick her up or shown any concern for her welfare. You left her to die.”
The 37-year-old, who was the duty baby room leader in charge of sleeping arrangements that day, told Manchester Crown Court she placed Genevieve on her side, claiming her face was visible at all times.
She said she had no concerns she was in any distress.
Jurors were in tears at the start of the trial as they watched the nursery CCTV footage which captured the tragedy unfolding from 1.35pm to 3.12pm.
The defendant’s case was that Genevieve’s death was a “terrible and unavoidable accident” and not the result of any unlawful acts.
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Roughley, of Heaton Norris, Stockport, joined Tiny Toes straight from college at the age of 18 and said she gained most of her knowledge of working with babies and young children from her colleagues.
She said the ratio of staff to children at the nursery “gradually worsened”.
In April and May 2022 the staff-to-children ratio was at various times one to nine, two to 11, two to 13 and one to 16, the court heard.