Nicole, I'm going to adopt your practice of writing from notes, because my memory is going!I just looked at Robert Bolling's 1764 Memoir and there's only one slim reference to the subject we're discussing: "He [Robert Bolling the immigrant] arrived here [Virginia] when only fourteen years of age, on 2 of October, 1660, and married, in the year 1675, Jane, daughter of Thomas Rolph, and grand-daughter of the Princess Pocahontas (wife of Mr. John Rolph), whose father was Powhatan, that Emperor of the Indians, who gave so much trouble to the English at their first establishment in his country."That's all -- nothing pro or con about the existence of other children.
It's not until 1887 that Wyndham Robertson, a one time Governor of Virginia, writes in POCAHONTAS AND HER DESCENDENTS, "Thomas Rolfe, b. 1615; d. 16__; m. Jane Poythress; left issue one child only, a daughter."But Robertson does not discuss how he came to this conclusion.And his selection of "Poythress" as Jane's family name may be shaky.
The successor volumes to Robertson's book -- POCAHONTAS' DESCENDANTS -- discuss Rolfe genealogy more fully.Although the editors seem eventually to come to the same conclusion as Robertson, it's clear to me that there's plenty of room for original research.But solid primary sources may be scarce or nonexistent.There's a reference, for example, drawn from the VIRGINIA MAGAZINE OF HISTORY AND BIOGRAPHY to a 1698 will referring to "Jane late wife of Robert Bolling" being "the only daughter of Thomas Rolfe, dec'd."But this is hardly conclusive evidence one way or the other and it's several decades "after the fact."
I'd be equally cautious (maybe more so) about historical markers that are several centuries "after the fact."Perhaps you can find out through the appropriate department of government how the marker itself came about and who provided the information it contains.I suspect it reflects the oral tradition of a well-known local family, which may be accurate or not.But if there are records of how the marker came about, maybe some interesting clues about the 17th century Rolfes will turn up.