The former Miss Universe contestant says she always believed that she would make it to the peak but doubts began to set in during the final hours as her pals began to suffer from altitude sickness.
Roz climbed the mountain with her model pals Lynn Kelly, Daniella Moyles and Emily MacKeogh last week.
And even though the 21-year-old says she was determined to climb the mountain no matter what, the Gosh cover girl says nothing could have prepared her for the final hike.
"I was lucky in that I didn't get any altitude sickness, some of the other girls did so I definitely got away with it. It wasn't easy but the first five days went along well.
"But nothing could have prepared me for the last day. It was definitely the hardest thing I have done in my life.
"We had a 14-hour hike to the summit and it was minus 25 degrees. There was ice in my hair and my hands were shaking with the cold," she said. And even though she kept pushing herself to complete the climb, which was in aid of the Make-A-Wish Foundation, Roz told the Diary she thought she may be forced to drop out of the hike when they got closer to the top.
"On that last day, we were hiking for six hours in complete darkness at one point. It was so cold and we were just climbing and climbing, the air was so thin, I remember thinking to myself I know I can make it to the top but I don't know now.
"My feet and fingers were so cold. I thought I might just collapse.
"There were 11 of us in the group in total and people were fainting, so I thought something might happen to me.
"But we got so far that we were never going to turn back, no matter what," she explained. Roz and the girls climbed the mountain in seven days, while being filmed for a new TV3 documentary, Catwalk To Kilimanjaro, which will air in the new year.
The cast enjoyed a well deserved party over the weekend.
While Roz decided to relax at home, her co-stars Emily MacKeogh, Daniella Moyles and Lynn Kelly celebrated completing their climb at Samsara Bar.