Hit 011, which is the number supposed to be pushed for all international calls, then 40, which is the Romania country code, and then the area code (2 or 3 digits), and finally the number, which is 6 or 7 digits.
To call Romania dial the US Exit code (011), followed by Romania's country code (40), the area code of the region you are calling, then the 6-7 digit phone number.
Dial 0040 for the international call prefix then country code, then you find the format depending on the city you are calling, so for instance you'd dial 004002yx-956 for gendarmerie.