Pelle, 29, scored the winner on debut last night against Euros qualifying opponents Malta.
Rossi, who brought through Pelle as Lecce coach, told TMW: "You could see he had great potential.
"During his time with Lecce, he had many qualities that needed to be polished, but Graziano is one that has done it alone, all he's received he's gained through work on the field.
"I'm really happy with the way his career has evolved, it means that if one believes, at the end the results will come."
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