Just started learning Japanese again. My college offers no class on this so I am learning on my own. I have been using Rosetta Stone on and off again for a while now.
One thing I have noticed is that Rosetta Stone uses は and を in basic sentences such as:
おんなのひとは、おちゃをのんでいます
This sentence gives the Romaji:
onna no hito wa ocha o nonde imasu
Now I know
Why would they use those in place of わ and お?
When being used as a grammatical particle ([助詞]{じょし}), は is pronounced わ (wa), を is pronounced お (o), and へ (which you may not have come across yet) is pronounced え (e).
I've never used Rosetta Stone but it seems quite strange that it would not mention this...
Information as to the historical reason for this difference between spelling and pronunciation can be found in the answer to this question.
Often the particle は is written "wa" in Latin letters, because は, when used as a particle, is in fact pronounced the same as わ. Of course, は, when it is not a particle, is usually pronounced "ha".
を is pronounced お, and therefore sometimes transcribed "wo" and sometimes "o".
Similarly, the particle へ is pronounced the same as え, whence "he" or "e".
For text input, you have to write "ha wo he" for は を へ, but for best pronunciation approximation, "wa o e" are often used.
So, as it should, Rosetta stone is writing correct Japanese and chooses rōmaji (not Romanji, see this question) for approximating pronunciation (presumably Hepburn romanization).
