I have a newspaper clipping from the Baraboo Public Library dated June 24, 1874, which states:
"MARRIED - NILES-GROUT - In Baraboo, June 20th, 1874, by John Dean; Esq. Mr. STILLMAN NILES and Mrs. JANE GROUT, both of Delton."
Maybe Rose was her maiden name as she is listed as a MRS.???? The wedding date seems to match exactly with other internet postings for his wedding to Rachel Rose.
Needs more looking into.