I don't know if you are still looking into the Robertsons.
I have Mathew (b 1804) marrying Sarah Custer James in 1820 in Jefferson IN. I show several sons: James, William (b 1828), Matthew and Jesse and a daughter Permelia.Both Mathew and William show up on the 1870 census in Tippecanoe IN. I also find William as a veteran of the Mexican War from Indiana.
I have William marrying Mary Jane Fairfield with a daughter Ella (b 1867, d 1950). She married my husband's ggfather Sanford Gay (1856-1935).His descent then goes to daughter Ester Gay (1890-1951), who married James Foster.
I'm interested in your research on this family. I have stuff on the Custers going way back, but nothing more on the Robertsons.