Mierce has a whole Kindred of Roman derivation the  Byzanti that might fit

https://mierce-miniatures.com/index.php?act=cat&cre=dkl-byz&sou=cat

and they work with their demon kindred the Inferni a fair few of whom have roman style shields

https://mierce-miniatures.com/index.php?act=cat&cre=dkl-ifn&sou=cat

I found Maveryc had Pax Bochemmanica as a skirmish game in the motif you want but not the size of force for Oathmark. Here’s a blog spot for the painted models.

I also found a 3D printing service that has a license for Roman themed Dread Elves. There is a command, legionaries, auxilia,  standard bearers and has options for shields.

My advice would be to look for Fantasy miniatures and swap a few bits out.  Remember that you can get away with a variety of armour types for a Roman look, doesn’t necessarily have to be Lorica Segmentata.

Recently I started putting together a collection of fantasy Greek themed Miniatures.  Obviously for humans I just used historical Miniatures.  For the Dwarfs I used Oathmark plastic dwarf heavy infantry but I switched out the weapons adding spears instead of the standard hand weapons, I bought a load of metal hoplite shields and I bought some heads from Puppets War.

Shown next to a Victrix plastic hoplite for scale

Back around the turn of the century there was one manufacturer who did a boxed set containing a “full unit” or 19 (19!) Dwarven Roman Legionares (with full command group). Unfortunately I can’t remember which company it was. I know it wasn’t Alternative Armies but it was around the time when Alternative Armies was a popular brand that all the hobby shops were stocking. I want to say it was around 2,001/2,002.

I’ve still got the box somewhere. I never glued them in the bases or painted them because 19 was a really awkward number to try to fit into a rectangular or square formation.

They were not the Dwarf Wars Roman Legion (which has 24 figures, an axe etc). These ones looked more Roman, if that makes sense. I think they might have been the ones from Black Tree Designs. This looks like them (not my paint job),. There was a short piece of descriptive/narrative text on the box about how this unit belonged to a dwarven commander who was experimenting with some new tactics. All the other dwarfs mocked them for looking so un-traditional but they stuck with their new tactics and got good results.

Also Hasslefree do a great Halfling version of Maximus Decimus Meridius (although they call him Minimus instead of Maximus).

@geometry dash unblocked it’s not late at all because it’s very impressive to me.

I did a unit of imperial goblin legionnaires. The warlord games plastic imperial romans are notoriously short minis but a perfect match for the oathmark goblin heads (and I also used some from wargames atlantic and the old wargames factory orcs).

The ‘veterans’ sprue is worth seeking out as it has battered shields and also the arm armour they used in Dacia.