Besides the 1851-1901 censuses (minus 81) and Reuben's marriage to Rosalina Coombe in Apr qtr 1889 in Devon, all of which I think you've got, have you seen Kelly's 1893 Directory for Plymouth, Devon: "Perkins Reuben tailor, 15 Saltash St, Plymouth"?

Also the 1911 census index gives:
"Rosalina Perkins born 1851, aged 60, widow, in Exeter district, Devon".
Neither gets you much further on, except I suppose it narrows the possible death date down.