They had moved into the house only a couple of days ago and it was now engulfed in fire.
"I just asked if there was anyone in there," Mr Ropata said.
"They said, 'Yeah, there's two more people - a young kid and a lady'."
Mr Ropata then heard the boy inside, and he entered the burning house without hesitation.
"Looking at [the boy's family], I knew they just weren't in the state of mind to go back in, so I did what anyone else would do. It was just adrenalin," he said.
It was darker inside the house than out on the street, with thick smoke blocking his vision.
"You could hardly see in front of you," he said.
But he could feel the intense heat coming from the fire - and he could hear the boy in a room.
"He was crying and screaming and banging on the walls."
Mr Ropata made his way to the boy, who was about 4 or 5 years old and in a state of panic.
"He didn't know where he was. He had just woken up to a fire."
Mr Ropata picked up the boy, who continued to cry while being carried outside. "I put him down and told him to go to the parents waiting for him."
Then Mr Ropata and his brother went around the side of the house to see if they could get to the woman still trapped inside.
"But it was too hot," Mr Ropata said.
"[It was hard] knowing someone's in there but knowing we couldn't do anything to save her."
The family were taken to Rotorua Hospital and treated for minor smoke inhalation.
They returned to their house late yesterday to take away what they could from the charred structure.
Mr Ropata knew little about them because they had just moved in, but they made brief conversation.
"They thanked us again.
"They were just glad they didn't have to bring out two bodies," Mr Ropata said.
"It just feels surreal.
"I didn't really think about [the danger].
"I just heard the little kid and it flicked a switch [inside me] and I went in."
Assistant Fire Commander Nigel Richards said an investigation into the cause of the fire had eliminated all causes other than smoking in bed.
"There was no other source of ignition in the location and unfortunately the deceased woman was known to smoke," Mr Richards said.
The woman would likely have been saved had there been a fire alarm installed at the property, he said.
"You might end up dying for your last cigarette.
"Whether you have just moved into your house, whether you have been in your house for 20 years, whether you are staying with friends, whether you are on holiday, for God's sake get yourself a smoke alarm, at least in your sleeping accommodation."
Smoke alarms were nearly always lifesavers, Mr Richards said.
"It is sad. They save lives and they save property too but that is a secondary thing.
"We are looking at saving lives."
The house was well alight when firefighters arrived and would probably be demolished.
additional reporting: NZPA
