In my post above "Robt A. WILLIAMS (b Mar 1835, d aft 1900) and Robt A. WILLIAMS (b 1840, d 1921)" I identified those Census records for each Robert A. WILLIAMS which I was able to locate, including the 1900 Census record you mention.
I made a fairly rigorous effort to locate the missing 1870 Census record without success.This included looking on EVERY page of the District 3, Lawrence County, Census returns for 1870.It is possible that those conducting the Census became confused about the presence of two contemporary Robert A. WILLIAMSes in the County and either neglected to survey both hourses or discarded field notes of one family thinking that it was a duplicate.
Similarly, I made a reasonably valiat effort to locate a 1910 Census record without success, leading me to believe that Robert WILLIAMS died or moved away before the 1910 Census enumeration.
It would seem to me that the appropriate approach would be to check the Lawrence County Probate and land records.These should indicate the presence of a Will or administration OR of the sale of family owned property.Similarly, any extant land tax records would tend to show continued ownership of the land.
This is the kind of detail that really needs to be researched using state or county archive records.
In my view, ROPER researchers have deprived themselves of much of what can be learned about the family and relationships by failing to make use of these basic primary resources.NOT EVERYTHING CAN BE FOUND ONLINE.
It is UNCLEAR to me whether you have posted Queries on WILLIAMS family message boards.It seems to me that WILLIAMS surnamed descendents may have had a keener interest in the burial place of their ancestors than collateral ROPER surnamed relatives.So posting on the WILLIAMS Messsage Board may be far more productive.
In my experience, you are far more likely to get a response if you include enough detail to make it LIKELY that a post might be found in an Internet search.Older message board posts otherwise quickly become lost in the clutter of additional board traffic.You might consider selectively copying and pasting some of the detail I posted in a focused query on the WILLIAMS message board, also cross-linking this message thread.
Separately, sometimes posting on the County Message Board can shake loose some information.While it isn't reasonable to expect someone to do a full genealogical investigation for you when you have a very focused question, such as WHEN Robert and Telitha DIED or MOVED AWAY, occasionally some local genealogist might have ready access and reference to a source not readily available, such as a compilation of work found only at a local genealogical society or in a local branch library.
These include tombstone inscriptions, deed abstracts, Will abstracts, probate record abstracts, etc.
A very specific query stating clearly what is KNOWN and what is being sought with one or more very specific question posted on the County Message Board might produce the missing data.Bear in mind that Robert A. WILLIAMS is shown to have been born in Alabama.Telitha ROPER's father James ROPER was also married in Lauderdale Alabama, which is adjacent to Lawrence County to the immediate South.
The primary commerce in that area would have been along the Tennessee River.
Secondary sources show James ROPER to have been buried at the Second Creek Church Cemetery.Since James ROPER is shown to have also resided in District 3, Lawrence County, almost adjacent to Robert WILLIAMS and his daughter Telitha Roper WILLIAMS, this seems to me to be a good place to look, if you haven't done so already.
The U.S. Geological Survey shows this information about the location of the Second Creek Cemetery:
Note that USGS cites as a source the book At Rest: Cemetery Records of Lawrence County, Tennessee, by Irene McBane Alexander and Carrie Hardwick Gresham (Lawrenceburg, TN.: Buffalo River Chapter Daughters of the American Revolution, 1977), p360.
This seems to me to be a source to consult.It is UNCLEAR whether there is only a description of the Cemetery or whether there are transcriptions of burial markers there.This might be something to ask about in a Query to the Lawrence County Message Boards.
Note the presence of Williams Road to the North and West of the Church and Cemetery?This seems UNLIKELY to me to be a coincidence!
I cannot emphasize enough that when looking for missing data, it is most useful to first establish that additional data which is EASY TO FIND.This includes the LOCATIONS of the family properties.Sometimes, the missing grave markers or on the old family properties and can be located by corresponding with the existing owners of those properties.