Apple - Is there a Mac OS X Command Line application that can convert text encodings from one type to another? (Specifically to convert Mac OS Roman to utf8)

iconv is definitively the tool of choice here:

iconv -f MACROMAN -t UTF-8 your-roman-encoded-file.txt > utf-8-encoded-file.txt

Run iconv --list to see a list of all supported encodings.

Another way to convert non-ASCII characters to ASCII variants is to use iconv -t ASCII//TRANSLIT:

$ echo ‘’“”–—…äé | iconv -t ASCII//TRANSLIT
''""--..."a'e

ASCII//IGNORE would remove non-ASCII characters, but you can also do that with for example tr -dc '\0-\177'.