Trajan Sans is very faithful to the inscription, but I don't know if you can really qualify it as "sans". Trajana Sans may be what you're looking for. I must say the charm of the subtle modulation of the roman inscription gets lost in the latter.

Also see http://typophile.com/node/61034.

. Lapidaria

Hmmm. The closest thing in my mind to that picture, is Throhand - Pen Roman, but Throhand - Pen Sans, that doesn't exist... and Throhand - Pen Dragon, but that's another story;)

Ok, how about slab serif sans?