You can type any roman worh in
http://www.xenomed.com/forums/unicode.php and it will convert all your roman into Nepali. But you will have to install Nepali font.
This Nepali can be copy and paste when you send mail or in the xenoMED but you won't see the font in notepad, word or power point and related places... you know why its becuase you haven't install "Nepali Keyboard Layout " in your computer
Most of us use windows XP so visit this page help you to learn as how you can install Nepali Keyboard Layout in your computer/Laptop:
http://mpp.org.np/detail_guide/winxp.htm
Once you follow all the instruction and install it you can paste the romanize typed Nepali anywhere in your computer, even you can write article, poem in Nepali with ease.