Ka cika wannan jumla: Ko da yake an haifi Rojas a Argentina, kakanninsa daga Paraguay ne. Ya yi fatan buga wa Argentina wasa amma tsananin gasa ya sa ya yi masa wuya ya taɓa samun kira, don haka ya zaɓi ya wakilci Paraguay a maimakon haka, kamar yadda ya bayyana a 1999: "Kakannina 'yan Paraguay ne kuma kafin na buga wa Argentina wasa, Na riga na sami kira don buga wa Paraguay. Duk da haka dai, na ki amincewa domin burina shi ne in buga wa tawagar Argentina wasa, amma ina jin kamar na san damar da nake da ita. Kafin gasar cin kofin duniya a Faransa, kungiyar kwallon kafa ta Paraguay ta sake gayyatar ni kuma na karbe shi kuma na wakilci Paraguay a gasar cin kofin duniya". An lissafa shi a cikin tawagar don
1997 Copa América, kuma ya kasance ɗan takara a gasar cin kofin duniya ta FIFA ta 1998, amma bai yi wani bayyanuwa ba. A duka, ya karbi kira 7 daga 1997 zuwa 1998.