A French friend pointed this out to me when we watched the 25th Anniversary Concert and she heard that dude shout "On-jol-rass", 'cept she said it nicely and simply.
Being a person with an often mispronounced name, and with his seriousness, I imagine that he'd eventually snap with annoyance. Am I right in saying his name isn't mentioned in the libretto?
Really, I don't think Ramin's the type to swear but I loved him as Enjolras and he pulled this great angry face and I couldn't resist
EDIT: As a few people (including the Les Mis film) have pointed out, the "s" can be pronounced as well, so I think it's up to preference whether that last part is said as "-rah" or "-rahs".