I am an Algerian national possessing a Serbian temporary residence. I want to travel from Belgrade to Romania, Bosnia and Montenegro. Do I need a visa for these countries?
You need a visa for Romania, as Algeria is own the list for the list of states whose citizens (annex 1), holders of simple passports, are required a visa upon entry on the Romanian territory.
You don’t need a visa for Bosnia if you stay less than 90 days:
Državljani Rumunije izuzeti su od viznog režima prilikom ulaska, izlaska ili prelaska preko teritorije Bosne i Hercegovine do 90 dana, u periodu od šest mjeseci, počevši od dana prvog ulaska.
(From the visa website)
Romanian nationals are exempted from the visa regime when entering, exiting or crossing the territory of Bosnia and Herzegovina for up to 90 days, for a period of six months, starting from the date of first entry.
You also need a visa for Montenegro, you can obtain it from the Serbian consulate. Details of the consulate available here.
You need a visa for Romania, ask your embassy. Their site is at: http://www.ambasada-algeriei.ro