Where Boughton refers to his and his first four children's place of birth as being Hancock, Massachusetts, it is more likely that the place was Hancock, Addison Co., Vermont.
The question remains as to what happened to his widow Mary (Frost) Rockwell after she moved to Genesee County, N.Y. Given that this detail appeared in an essay about her son Dennis (R154), I wonder if she moved to Washtenaw County, Michigan, with him. If so, there may be a reference to her death in an old diary now transcribed on the Web. Shirley Johnson, who has ancestral links to Washtenaw County through a different branch of the John line, found a reference the transcript of "The diary entries of John Geddes of Washtenaw County, MI - 1849" at https://sites.rootsweb.com/~miwashte/ged1849.html An entry for 15 Sept. 1849 reads: "Mrs. Rockwell died to day aged 74 or 75 years." As this woman was too old to be part of several other Rockwell families, I wonder if this is Dennis's mother Mary. On the other hand, this individual may be of another family altogether.