ROSEB Initiative covers three bordering regions from Serbia, Romania and Bulgaria:

• East Serbia
• North West Bulgaria
• South West Romania

Joint cross-border region have 2.191.000 inhabitants in total.

The area considered as the eastern Serbia is consisted of territories of Bor and Zajecar districts which includes municipalities: Majdanpek, Kladovo, Negotin, Bor, Zaječar, Sokobanja, Boljevac and Knjaževac. Region has 242.000 inhabitants.

Northwest Bulgaria region is consisted of:

• Districts Vratsa, with municipalities Vratsa, Borovan, Byala Slatina, Kozlodui, Krivodol, Mezdra, Miziya, Oryqhovo, Roman and Hayredin.
• District Montana with municipalities Montana, Berkovitsa, Boychinovtsi, Brusartsi, Valchedram, Varshets, GeorgiDamyanovo, Lom, Medkovets, Chiprovtsi and Yakimovo.
• District Vidin with municipalities Vidin, Belogradchik, Boynitsa, Bregovo, Gramada, Dimovo, Kula, Makresh, Novo selo, Ruzhintsi and Chuprene.

Region has 435.000 inhabitants.

The area considered as the South West Romania consist of the counties Mehedinti, Dolj and Olt (south of Oltenia Region). 
Region has 1.514.000 inhabitants: 306.000 in Mehedinti County, 720.000 in Dolj County and 488.000 in Olt County.

The ROSEB area is characterised by some additional features, which can be summarised as:

• Coverage of a large area with a high diversity of regions and often conflicting interests;
• Full Integration into a Macro Region framework, the Danube Macro Region, which generates substantial challenges and opportunities of coordination and synergies.