I had a look on Romanian Foreign Affairs Ministry page and they say that Romanians do need visa for entring in Bolivia.
Unfortunately, Bolivia does not have an embassy in Romania, the Ministry says that one can go to Berlin or Vienna to get it, an option which I don't like too much.
I found out that one can get the visa on arrival but for a fee, if you get it before it is free.
I will pass through Argentina and Chile before going to Bolivia so my plan is to get it from the Bolivian Embassy in Buenos Aires or Santiago. Is it possible?
Also about Chile, here says that
Due to strained relations with Chile, Bolivia only has Consulates-General in Chile.
Are they able to give an entry visa in this case?