sand

ash

ground nut shells or crushed fruit pits(I used to used ground peach pits, it was a "thing" you could buy)

pumice stones

I agree with sand.

A tool or knife to scrape off dirt before bathing.

Lady Romans

For a minute there when I first looked at the answer, I thought my 3rd guess was going to be right. Now that would have been funny! ! !

Sorry, Jasdip, the devil made me do it. LOL!

Today's guess, water, then oil and a knife-like tool to scrape the dirt and oil off.

A communal sponge.

Rusty

In the movie, Sebastiane 1976, the Roman soldiers used water, then olive oil and a knife-like tool to scrape it off, as Rusty said. Maybe she saw this movie. In this movie, the soldiers washed each other, as it would be difficult to wash one's own back this way.

Fels Naptha. It's been around forever.

Lars, I had to Google that movie, no, I've not seen it, doesn't sound like one I would like. At one point in my life I was very interested in anything that had to do with life in Rome in ancient times. I have no idea where or when I read or saw anything connected to their bathing methods, but it's one of those weird facts that has stuck with me.

Rusty