You have a lot of company among those trying to figure out the sources for material accumulated by or at behest of a deceased relative.Such material often has odd gaps and conclusions taken for unknown reasons (so often, the most common genealogical mistakes: "same name = same person" and/or "same surname = same famiy").
Not infrequently such material jumps a few generations based on the above misconceptions in combination with a desired "history" that is not necessarily based in fact.
Sidebar: the family of one of my distant cousins paid to have a biography published in one of the "County History" type books, that gave some genealogical material.Some was mistaken (skipped one near ancestor).Some was pure fantasy -- skipped back some 200 years to assert that ancestry was from an unstated individual who settled in Jamestown, VA.This was more attractive to a WV family ca. 1910 than that the earliest known patrilineal ancestor came to WV from DE in 1796.
If your great-gran did not give the name of this purported ancestor and document the connection, how could she know what his Rev. War service was?
You can take a look at extracts by the National Park Service from Rev. War rolls of units believed to have been at Valley Forge, here (click on the 'Muster Roll' link to get a search page):
For individuals who look to be of interest you can look at Compiled Service Records on www.footnote.com or on www.ancestry.com, look at microfilmed images of the actual rosters on ancestry.com or borrow the microfilm for a particular unit through your local library's inter-library loan service.A list is here for the microfilm roll numbers for particular regiments within National Archives Micropublication No. 246 (immense thanks to John K. Robertson and Bob McDonald for this):
Note that military records hardly ever have any information that is directly genealogically helpful.But if a man was killed in action his widow might apply for support from the County (research necessary personally in County Court records), and some wives with little children applied for some support from the County while the husband was away -- such records are not common, but sure do help make a connection between a soldier and his family/residence.Quite rarely the 'size rolls' survive, a description of the recruit's appearance, home and occupation that was made to ease finding a person if he deserted; these also are genealogical gold.