| - go to control panel - regional settings - languages - details, then press 'add' button, the dialog appears, where you can choose a language and a keyboard.
note there's no need to set the strict correspondence between the language and the keyboard.
for example, i have two input languages and keyboards installed - english and russian, and i switch between them with alt-shift. initially i added romanian keyboard with the romanian language and got three languages and had to cycle through them with alt-shift, which was not convenient since i use a lot the russian and the english keyboards and get used to switch between them with only one keypress, so an additional language interfered with. so i deleted the romanian language with the keyboard and added additional keyboard to the english language (i.e. i still had two languages but one of them had two keyboards) and swithched between the keyboards with ctrl-shift. so everything works fine since then %)
if you have additional languages, besides of the english, you can adapt my approach. or if you have only english, you can install romanian as a different language, not as an additional keyboard for english.
additional letters are on the following keys - [ ] \ ; ' (additional keys on the right end of the letter rows, the placement of \ may vary)
note that the placement of y and z on the romanian keyboard is kind of confusing - they are just interchanged.
the placement of the symbols is completely different (only , and . placed as on english keyboard)