I can't find them after the 1920 Census when they're in Osage Co., OK. I'm sure you already know this but the challenge in Oklahoma is that they don't print a death index. Therefore, deaths have to be found in cemetery records, obituaries, funeral homes, etc.
I found the following:
01-353-03, Brown, Rosetta, Buried June 22, 1974, Peter Funeral Director. the numbers refer to SC-Lot-Sp Source: Osage Gardens Cemetery, Skatook, Osage Co., www.usgwarchives.net/ok/osage/cemtery.htm Click on Osage Gardens Cemetery A-D
The various funeral homes in Osage Co. are listed at www.okcemeteries.net/osage/funeralhomes.htm.
I looked through all cemeteries that are indexed online but they aren't all indexed and some of the indexes are partial.
There isn't a genealogical society in the county. I'd contact the Osage County Historical Museum, www.osagecohistoricalmuseum.com/ and see if they have a complete list of cemeteries and who is buried where.
You can order a copy of a death certificate in Oklahoma but you must fill in where and when the person died. For more details, go to Oklahoma State Dept of Health, www.ok.gov/health/Birth_and_Death_Certificates/Death_Certif...