There is no any proves, that NATO attacks thru Romanian and Bulgarian aerospace...
F-117A regularly used Romanian airspace when they approached Belgrade from east.
Vega-31 Dale Zelko come from Aviano - Slovenia - Hungary (refuel/Stealth up) - Romania that night, bombed South of Belgrade arriving from east, than turned back to north towards his tanker, waiting above Hungary...
... just listen his podcast.
http://www.af.mil/shared/widgets/radio.asp?cid=129%26sid=8531