I found the following death dates:
Death 20 Jan 1920
Death 7 Jan 1938 Council Bluffs, Pottawattamie, Iowa, USA
I am searching for verification.
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1870 United States Federal Census
Name: R W Ropp
Age in 1870: 7
Birth Year:
Birthplace: Iowa
Dwelling Number: 29
Home in 1870: Franklin, Marion, Iowa
Race: White
Gender: Male
Post Office: Knoxville
Occupation: At Home
Inferred Father: Jno Ropp
Inferred Mother: P Ropp
Household Members:
Name Age
Jno Ropp 45
P Ropp 41
E Ropp 18
M C Ropp 17
J B Ropp 15
C Ropp 13
W H Ropp 11
R W Ropp 7
J E Ropp 5
L M Ropp 1

1880 United States Federal Census
Name: Robert W. Ropp
Age: 16
Birth Date: Abt 1864
Birthplace: Iowa
Home in 1880: Franklin, Marion, Iowa, USA
Dwelling Number: 377
Race: White
Gender: Male
Relation to Head of House: Son
Marital status: Single
Father's Birthplace: Pennsylvania
Mother's Name: Priscilla Ropp
Mother's Birthplace:
Occupation: Farms
Attended School: Yes
Household Members:
Name Age
Priscilla Ropp 50
William H. Ropp 21
Robert W. Ropp 16
Fannie E. Ropp 14
Lillie May Ropp 11

Iowa, Select Marriages Index, 1758-1996
Name: Robert W. Ropp
Gender: Male
Marital status: Single
Birth Place: Marion Co., IA
Marriage Date: 23 Nov 1887
Marriage Place: Denison, Crawford, IA
Father: John Ropp
Mother: Percilla Elder
Spouse: Minie A. Dyson
FHL Film Number: 1035130
Reference ID: 2:3BP06SX

Iowa, State Census, 1895
Name: Robt W. Rapp
Age: 28 (born abt 1867)
Race: White
Birthplace: Monroe Co IA
Residence: Comieel Bluffs;Kane, Pottawattamie

Iowa, State Census, 1895
Name: Minnie Rapp
Age: 26 (born abt 1869)
Race: White
Birthplace: Ills
Residence: Comieel Bluffs;Kane, Pottawattamie

Iowa, State Census, 1895
Name: Charles Rapp
Age: 7 (born abt 1888)
Race: White
Birthplace: Cranford Co IA
Residence: Comieel Bluffs;Kane, Pottawattamie

Iowa, State Census, 1895
Name: Eue Rapp (Earl)
Age: 5 (born abt 1890)
Race: White
Birthplace: Neb
Residence: Comieel Bluffs;Kane, Pottawattamie

1900 United States Federal Census
Name: Robert W Ropp
Age: 35
Birth Date: Jul 1864
Birthplace: Iowa, USA
Home in 1900: Kane, Pottawattamie, Iowa
Ward of City: 3d
Street: Main
House Number: 919
Sheet Number: 2
Number of Dwelling in Order of Visitation: 32
Family Number: 36
Race: White
Gender: Male
Relation to Head of House: Lodger
Marital status: Widowed
Marriage Year: 1900
Years Married: 0
Father's Birthplace: Iowa, USA
Mother's Birthplace: Iowa, USA
Occupation: Day Laborer
Months Not Employed: 2
Can Read: Yes
Can Write: Yes
Can Speak English: Yes

1910 United States Federal Census
Name: Robert W Ropp
Age in 1910: 40
Birth Year: abt 1870
Birthplace: Iowa
Home in 1910: Omaha Ward 3, Douglas, Nebraska
Street: Farnam Street Card
Race: White
Gender: Male
Relation to Head of House: Lodger
Marital status: Single
Father's Birthplace: Germany
Mother's Birthplace: Germany
Native Tongue: English
Occupation: Laborer
Industry: Smelting Works
Employer, Employee or Other: Wage Earner
Able to Read: Yes
Able to Write: Yes
Out of Work: N
Number of weeks out of work: 0