I've been dying to ask this for years. I've tried several on-line translators, but it never makes much sense to me, some of them do not even translate all of the words, so I have had to look them up seperately. I have had to guess at the proper meaning. Anyway, this is the phrase that is at the very end of A Study in Scarlet:

"Populus me sibilat, at mihi plaudo
Ipse domi simul ac nummos contemplar in arca."

This is my latest rough translation:
"People hiss at me, at my applause
His home and money, observe in the chest."

I think he is referring to the fact that he just gave both of the official detectives a boost in their jobs/accolades in the press but at home his wealth remains the same? I am really not sure. It would been really nice of ACD to tell us which "Roman miser" he was referring to, then I would have been able to search that way. Anyway, thanks for your help!