По обсуждаемой теме написано как раз абсолютно конкретно.
http://www.mae.ro/en/node/2040
**Holders of permanent residence permits issued by member states of the European Union may enter and reside in the territory of Romania for up to 90 days, within a period of 6 months, without a Romanian visa.
The above-mentioned residence permits must be issued in keeping with the provisions of Council Directive 2003/109/EC concerning the status of third-country nationals who are long-term residents, according to which the residence permits issued to third-country nationals having the status of long-term residents in one of the member states of the European Union, must be valid for a period of at least 5 years.
Article 8 (3) of the above-mentioned Council Directive states that, under the heading “type of permit”, the residence permits issued to long-term residents must read “LONG-TERM RESIDENT - EC”.
All the permits that do not fall into this category are not long-term residence permits and hence, the holders of such permits must apply for a Romanian entry visa.