Found on the walls of an ancient Pompeiian villa, this fresco clearly reveals to the incredibly credulous that lesbian mistresses violating beautiful young slave girls with strap-ons were a thing in ancient Roman times.* Who knew? Image source: Whipped Ass.com.
The issue of whether or not ancient Roman women used strap-on dildoes is difficult to discover via Google, as any search with those key terms will turn up many, many porn sites whose answer is an enthusiastic "Yes!" but fail to back it up with anything but many, many, many videos and photos of modern women engaging in lesbian activities.
I found exactly one site that had actual cites, but they were mostly in the form of cites to books, not links, so I could not verify it but it seems kind sound so I'll cite it.
My considered answer is "Yes," this did occur, based on the link cited and what I've read in general articles about the treatment of slaves in the ancient world. If ancient Roman lesbian women had dildoes, some of them undoubtedly used them on their slave girls, there was very little in the Roman ethos about sexuality or the treatment of slaves to stop them. The freize above is a phtoshopped fake, based on the image below. It stuck me that Isis Love's pose had an "ancient world" vibe to it so I went with it. Who can blame me, really?
Isis love gives a blonde and bound Kink.com model a thorough pegging in this photo from Whipped Ass.com.
*This fake image proves no such thing, but that doesn't mean it didn't happen!