Nora, I tried your email address but the message bounced back.
I have the text of Harrison Johnson's Obituary from "The Marble Rock Journal" sent to me by the Historical Society and tried to forward you this text. It clearly states that he was an orphan by age 12, which put put his parents as having died about 1855. The obit states that he went to Canada in 1859 to 1965 before coming to Marble Rock, Iowa.
I see that there are two, and I don't know if Royal C. Johnson was enumerated twice, but the census data was taken on the same day, June 3 1880. I guess it's possible. I can't believe how many Johnson's there are with the first name 'Royal'. In the Obituary, Martin Levi is listed as 'Levi' Johnson from Blue Earth MN.
Send me your email address to firstname.lastname@example.org and I will try to send the Obituary again.