With a cemetery this old, the markers were probably carted off for construction a long while ago. In that "Secret File of Marco Polo" docu I watched the other day, they showed the Christian gravestones in China from his era, and that's what happened with those. Mary Beard's Roman docu's are on YouTube, and she visits some interesting burials and related monuments.
What's truly a shame is that large sections of Hadrian's Wall remained mostly intact for 1600 years, only to almost entirely disappear in the 1700s when an English general running from sea to sea along the Scottish border slaughtering all the Scottish soldiers he could find, decided he needed a paved road to speed up his troop movements, and dismantled most of what was left of the Wall to use the stones for that purpose.