There are several ways to type Romanian; it depends on what you are doing.
You do need adequate fonts installed. Any modern Linux distribution already comes with such fonts installed.
These days, any font that has good support for Unicode Latin character set will do. (Unicode has superceded support for the character set "ISO 8859-2 Central and East European").
If you want Romanian to be your primary system language, so that system menus, messages, icons etc are in Romanian, that can be done. In most Linux distributions, you can also set the system language, under "System Settings" -> Languages. But I find it's best to start out by installing the system clean with Romanian support.
If you just sometimes want to type in Romanian using a standard Romanian key layout, that is easy in modern Linux distributions. For example, my system has under the main GUI Menu "System Settings", where there is a "Keyboard" applet, which has a "Layouts" tab. There you can add a keyboard for Romanian. On my system, I get an icon on my task bar that switches from one keyboard layout to another.
If you mostly type U.S. English (for example), and just occasionally want to type Romanian words without messing with a Romanian keyboard layout, it might be better to set up "compose keys". This is also easy: under "System Settings" -> Keyboard -> Layouts, choose "English (US)". Then click the Options button. In the list that appears is an item "Position of Compose Key". I set this to be the "right alt" key.
This should allow you to use the "compose-key" to type Romanian letters. You hold down the "compose key" (in the above instructions, the "right alt" key), type a special key, then the letter you want, to form a combined letter:
Code:
ț (<compose> ;) t
î (<compose> ^) i
ă (<compose> U) a
Note the ^ and the U require the shift key to be held down, as well as the compose-key.
This has the advantage is that on an English keyboard, the compose-keys remind you of the mark to be applied:
; for below comma (well, really it should be a comma, but that was already taken for the cedilla)
^ for circumflex
U for breve
It also has the advantage that you can type special letters from many languages.
Do a search for "Linux compose key sequences".
Cheers!