First name of “Mary” and year of death of “1936” from:
https://en.wikipedia.org/wiki/Ben_Roberts_(politician)

Maiden name of “Baker”, date and place of marriage (Hunter Street Methodist Church, Chester), name and occupation of her father, from page 15 and 146 of the biography of Mary’s husband, Ben Roberts:
“Remembered - From Ploughboy to Parliamentarian, The life and works of the Hon. Ben Roberts, Minister of Agriculture and Marketing 1943-46”.

On page 16, “they had three sons and a daughter”.

On page 17 of “Remembered…”, Ben and Mary with children emigrated to New Zealand aboard the SS Fifeshire, arriving in Wellington on Christmas Eve 1907. They settled on a property called “Lowlands” in Featherston in the Wairarapa, North of Wellington. Later, he bought a house and 10 acres in Carterton. Then in 1916 he leased 100 acres at Parkvale, six miles from Carterton. Ben and Mary had seven children by this stage.

Date of death from Obituary Notice for Mary from Papers Past found in August 2023:
Pahiatua Herald, 29 AUGUST 1936, page 6.
M.P.'S WIFE DEAD.
MRS BEN ROBERTS OF MASTERTON
Electric Telegraph - Press Association CARTERTON. This Day.
The death occurred at a private hospital early this morning of Mr. Mary Roberts, wife of Mr Ben Roberts, M.P. for Wairarapa, aged 57. Deceased had been ill for a few weeks and leaves a family of three son and four daughters.

Estimated year of birth from death search on New Zealand BDM website in August 2023:
1936/21342. Roberts, Mary. Died age 57Y [Therefore born circa 1879]

Full date of death of 29 August 1936 from further searching in August 2023 on BDM Search by incrementally changing the date range for the death.

Date of birth, different birth place, different date of death, place of burial, from Find a Grave website found in September 2023:
https://www.findagrave.com/memorial/162410666/mary-roberts
Name: Mary Roberts
Maiden Name: Baker
Birth Date: 18 Nov. 1879
Birth Place: England
Death Date: 3 Aug. 1936
Death Place: Carterton District, Wellington, New Zealand
Cemetery: Clareville Cemetery, Clareville, Carterton District, Wellington, New Zealand

Is this a record of Mary Baker's birth, giving more exact place of birth, found in the England & Wales Civil Registration Birth records in September 2023:
Name: Mary Baker
Registration Quarter: Oct-Nov-Dec 1879
Registration Place: Wrexham, Denbighshire, Wales
Volume: 11b
Page: 276

More exact place of birth, names of parents and older siblings from the 1881 Wales Census taken on the night of 3 April 1881 for the Holt, Denbighshire, Wrexham, Wales found in September 2023:
Road: Common Wood
James Baker, Head, Married, age 48, Brickmaker and Farmer, Born Carden Cheshire England [circa 1833]
Harriet Baker, Wife, Married, age 46, Farmer's wife, Born Crewe Cheshire England [circa 1835]
Emma Baker, Daughter, Unmarried, age 27, Farmer's Daughter, Born Farndon Cheshire England [circa 1854]
James Baker, Son, Unmarried, age 25, Brickmaker, Born Crewe Cheshire England [circa 1856]
George Baker, Son, Unmarried, age 18, Carter, Born Crewe Cheshire England [circa 1863]
Elizabeth Baker, Daughter, Unmarried, age 16, General Servant (out of situation), Born Burton Wrexham Denbighshire Wales [circa 1865]
Thomas Baker, Son, age 14, Brickmaker (apprentice), Born Burton Wrexham Denbighshire Wales [circa 1867]
William Baker, Son, age 12, Brickmaker (apprentice), Born Holt Denbighshire Wales [circa 1869]
Eliza Baker, Daughter, age 11, Scholar, Born Holt Denbighshire Wales [circa 1870]
Hannah Baker, Daughter, age 9, Scholar, Born Holt Denbighshire Wales [circa 1872]
John Baker, Son, age 7, Scholar, Born Holt Denbighshire Wales [circa 1874]
Harriet Baker, Daughter, age 7, Scholar, Born Holt Denbighshire Wales[circa 1874]
Catharine Baker, Daughter, age 5, Scholar, Born Holt Denbighshire Wales [circa 1876]
Mary Baker, Daughter, age 2, Born Holt Denbighshire Wales [circa 1879]

Entry in the 1891 Wales Census taken on the night of 5 April 1891 for the Holt, Denbighshire, Wrexham, Wales found in September 2023:
Road: Big Common Wood
James Baker, Head, Married, age 58, Brickmaker, Born Carden Cheshire England [circa 1833]
Harriet Baker, Wife, Married, age 56, Born Crewe Cheshire England [circa 1835]
William Baker, Son, Single, age 22, Brickmaker, Born Common Wood Holt Denbighshire Wales [circa 1869]
Hannah Baker, Daughter, Single, age 19, Born Common Wood Holt Denbighshire Wales [circa 1872]
John Baker, Son, Single, age 17, Labourer in Brickyard, Born Common Wood Holt Denbighshire Wales [circa 1874]
Harriet Baker, Daughter, age 17, Born Common Wood Holt Denbighshire Wales [circa 1874]
Catharine Baker, Daughter, age 15, Scholar, Born Common Wood Holt Denbighshire Wales [circa 1876]
Mary Baker, Daughter, age 12, Scholar, Born Common Wood Holt Denbighshire Wales [circa 1879]

Entry in the 1881 Wales Census taken on the night of 3 April 1881 for the Holt, Denbighshire, Wrexham, Wales found in September 2023:
Road: Common Wood
James Baker, Head, Married, age 48, Brickmaker and Farmer, Born Carden Cheshire England [circa 1833]
Harriet Baker, Wife, Married, age 46, Farmer's wife, Born Crewe Cheshire England [circa 1835]
Emma Baker, Daughter, Unmarried, age 27, Farmer's Daughter, Born Farndon Cheshire England [circa 1854]
James Baker, Son, Unmarried, age 25, Brickmaker, Born Crewe Cheshire England [circa 1856]
George Baker, Son, Unmarried, age 18, Carter, Born Crewe Cheshire England [circa 1863]
Elizabeth Baker, Daughter, Unmarried, age 16, General Servant (out of situation), Born Burton Wrexham Denbighshire Wales [circa 1865]
Thomas Baker, Son, age 14, Brickmaker (apprentice), Born Burton Wrexham Denbighshire Wales [circa 1867]
William Baker, Son, age 12, Brickmaker (apprentice), Born Holt Denbighshire Wales [circa 1869]
Eliza Baker, Daughter, age 11, Scholar, Born Holt Denbighshire Wales [circa 1870]
Hannah Baker, Daughter, age 9, Scholar, Born Holt Denbighshire Wales [circa 1872]
John Baker, Son, age 7, Scholar, Born Holt Denbighshire Wales [circa 1874]
Harriet Baker, Daughter, age 7, Scholar, Born Holt Denbighshire Wales [circa 1874]
Catharine Baker, Daughter, age 5, Scholar, Born Holt Denbighshire Wales [circa 1876]
Mary Baker, Daughter, age 2, Born Holt Denbighshire Wales [circa 1879]

Living with widowed sister in the 1901 Wales Census taken on the night of 31 March 1901 for the Holt, Denbighshire, Wrexham, Wales found in September 2023:
Street: Common Wood, Plas Devon.
Ann Jones, Head, Widow, age 39, Farmer, Own account, Born Holt Denbighshire Wales [circa 1862]
Mary Baker, Sister, Single, age 22, Born Holt Denbighshire Wales [circa 1879]
[NOTE: Mary married Ben Roberts five and a half months after this 1901 Census].

Shows an older sister of Mary called “Ann” confirming above 1901 Census entry - this from the 1871 Wales Census taken on the night of 2 April 1871 for the Holt, Denbighshire, Wrexham, Wales found in September 2023:
Road: Big Common Wood
James Baker, Head, Married, age 38, Farmer of 50 acres and Brickmaker, Born Carden Cheshire England [circa 1833]
Harriet Baker, Wife, Married, age 36, Farmer's wife, Born Crewe Cheshire England [circa 1835]
Emma Baker, Daughter, Unmarried, age 17, Farmer's Daughter, Born Crewe Cheshire England [circa 1854]
James Baker, Son, Unmarried, age 15, Farmer's Son, Born Crewe Cheshire England [circa 1856]
Ann Baker, Daughter, age 9, Scholar, Born Crewe Cheshire England [circa 1862]
George Baker, Son, Unmarried, age 7, Scholar, Born Crewe Cheshire England [circa 1864]
Elizabeth Baker, Daughter, Unmarried, age 5, Scholar, Born Burton Wrexham Denbighshire Wales [circa 1866]
Thomas Baker, Son, age 4, Scholar, Born Burton Wrexham Denbighshire Wales [circa 1867]
William Baker, Son, age 2, Born Holt Denbighshire Wales [circa 1869]
Eliza Baker, Daughter, age 6 months, Born Holt Denbighshire Wales [circa October 1870]

Record and reference of marriage to Benjamin Roberts from England and Wales Civil Registration Marriage records found on October 2023:
Groom: Benjamin Roberts
Bride: Mary Baker
Names on Page: Benjamin Roberts, Mary Baker, Ann Eliza Bradley
Registration Quarter: Jul-Aug-Sep 1901
Registration district: Chester, Cheshire
Volume: 8a
Page: 834

Photo of headstone from the Regulatory & Licensing Administrator of the Carterton District Council in June 2024:
Sacred to the Memory of
Mary
Beloved Wife of
Benjamin Roberts
M.P. Wairarapa
Who passed away
August 1936
To live in the Hearts of those we leave
behind. Is not to die.

Sacred to the Memory of
Benjamin Roberts
M.P.
Minister of Agriculture
and Marketing
1943 - 1946
He loved God his fellow
Men and the Good Earth
Died 1952
Aged 72 Years