Citizens of the states which are not part of the European Union or of the European Economic Area and wish to travel to Romania for a brief period of time, must obtain an entry visa in case they come from a State for which visas are required.
More details at https://www.mae.ro/en/node/2035#null
ANNEX 1 - list of states whose citizens, holders of simple passports, that are required a visa upon entry on the Romanian territory (https://www.mae.ro/sites/default/files/file/anul_2018/2018.11.28_anexa_1_en.pdf)
The conference attendees from the RUSSIAN FEDERATION should apply for visa (according to the CE 539/2001 regulation).
You need a short-stay visa for scientific activities (marked C/ZA), that can be issued by the Romanian consular services in Moscow (http://www.mae.ro/en/romanian-missions/3222#783) or Sankt Petersburg (http://www.mae.ro/en/romanian-missions/3278#783).
The document required by the consular services is a written request from the host organization (http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=CELEX:22007A0517%2801%29:EN:HTML).
IFIN-HH will issue this document if the conference organizers are contacted at icasc2019 at nipne dot ro.
ANNEX 2 - list of states whose citizens, holders of simple passports, are not required a visa to travel to Romania (https://www.mae.ro/sites/default/files/file/anul_2018/2018.11.28_anexa_2_en.pdf)
Categories of nationals also exempt from the requirement to be in possession of a Romanian short-stay visa are:
Holders of biometric passports, nationals of the following states:
- Republic of Moldova
- Former Yugoslav Republic of Macedonia
- Republic of Serbia, except for the passports issued by the Serbian Coordination Division (in Serbian: Koordinaciona uprava)
- Republic of Montenegro (the non-biometric passports issued by this state are no longer valid)