Lol, excuse me?
They never exterminated nor expelled all the Non-Serbs from Voivodina. There are like 250.000 Hungarians over there and Hungarian is one of the official languages together with Serbian, Romanian, Slovak, Croatian and Panonnian Rusyn. I even know personally Hungarians from there. And they didn't took Voivodina, that was a reward given to Serbs by the Antante after Austro-Hungary lost WW1. Same as we got Transylvania.
Here is your Wikipedia
https://en.wikipedia.org/wiki/Vojvodina
Regarding Romanians and Vlachs from Serbia, as i said, Serbs never had any problem with them too. They always coexisted in harmony.