Ceausecu gets a head injury, and starts launching massacres right before the fall of the Iron Curtain. The USSR and other countries neighboring Romania will be in too much upheaval to do anything about it, but still threatening enough that NATO doesn't want to intervene within their sphere of influence.
Even if he was one step away from being the Kim Il-sung of Europe (should've gone for a Songun "military first" sort of thing to better suppress the Romanian Revolution), I don't think you'd get much more than a Romanian Civil War (Syria-style, a lot of people dead, but the regime still powerful) at worst, and definitely not the sort of mass brutality of Pol Pot. Romania was too industrialised to even dream about ideas like "let's empty out the cities and put a bullet in anyone's head who resists" (or really just beat anyone to death who resists, since bullets were too expensive to regularly kill people with). Ceausescu wanted Romania to be a strong country, and didn't want Romania to be a Soviet puppet, and especially didn't like Romania's neighbours like Hungary. If you empty everyone out into the countryside, you won't be able to get the nuclear weapons to safeguard the regime. And it might even stop you from making a move against Moldova or Northern Bukovina (integral Romanian land) if the opportunity presents itself.
Pol Pot's ideology was a product of Khmer nationalism (Angkor Empire was great, until those damned Vietnamese, Thai, Chinese, and Europeans came in!) mixed with third-world communism. It's very hard to imagine such a combination occurring in 20th century Europe and producing similar results. I don't think you'd see something like that outside of places like Cambodia or other smaller, less developed Asian countries, Africa (Macías Nguema of Equatorial Guinea did similar things), and perhaps Latin America. The historic conditions in Europe in the 20th century don't seem fertile to produce an ideology like the Khmer Rouge, let alone have a man like Pol Pot be able to put it into action and kill that many people.