The death happened at Hamerton Zoo Park, near Huntingdon, at about 11:15 BST on Monday.
Friend Garry Chisholm, a wildlife photographer in his spare time, said she was the "focal point" and "shining light" of the wildlife park.
The zoo said it was a freak accident, and police said it was not suspicious.
Mr Chisholm, 59, of Irchester, Northamptonshire, said the wildlife park revolved around the zoo-keeper.
"Rosa wasn't just a keeper at Hamerton Zoo - she was Hamerton Zoo," he said.
Rosa King, pictured in 2016, was killed by a tiger
"She was the absolute central point of it, the focal point of it. She was the shining light of it.
"Her passion for the animals in her care was exceptional though her favourites were undoubtedly the cheetahs which she would refer to as her pride and joy.
"She will be greatly missed, not just by me, but by everyone who came to know her.
"The only consolation I can take from today's tragic events is that Rosa is now reunited with her beloved Ares the cheetah, and Blizzard and Ladybelle, her beloved tigers."
A Cambridgeshire Police spokesman said: "A tiger had entered an enclosure with a keeper. Sadly the female zoo keeper died at the scene."
Visitors were led away from the zoo. At no time did the animal escape from the enclosure, said police.
Officers investigating the death said it was "not believed to be suspicious", and that the tiger involved was "believed to be fine".
An air ambulance landed at the wildlife park but there were no other injuries
Hamerton Zoo Park said in a statement: "This appears to have been a freak accident.
"At no point during the incident did any animals escape their enclosures and at no point was public safety affected in any way.
"All our thoughts and sympathies are with our colleagues, friends and families at this dreadful time.
"The park will be closed from tomorrow, 30 May, and we will give more information as soon as we can."
The wildlife park said an investigation was under way.
A visitor to the zoo, who did not wish to be named, told the BBC: "We got to the zoo at opening time, around 11:45.
"We were close to the tiger enclosure when a member of staff shouted for everyone to leave the park quickly and immediately."
Hamerton Zoo Park
The wildlife park opened in June 1990 and covers 25 acres.
It includes enclosures for Malaysian tigers, Bengal tigers, cheetahs, wolves, corsac foxes, kangaroos as well as a variety of birds, reptiles and domestic animals.
The zoo opened a new enclosure for its Malaysian tigers in July last year.
In October 2008 a cheetah which escaped from the park was found by a nine-year-old boy in the back garden of his family home.