The seven-time world champion will make his first appearance in the series since 2012 at this weekend's three-hour Endurance round at Imola, having announced his retirement from MotoGP last August.
He has joined Vosse's WRT Audi team that clinched the GTWCE overall and Sprint Cup titles last year with Dries Vanthoor and Charles Weerts. Rossi will contest the full GTWCE Sprint and Endurance schedule alongside Audi factory driver Frederic Vervisch, with Nico Muller joining them for the longer races.
Rossi enjoyed “a good day of testing” last month at Circuit Paul Ricard, getting within four tenths of the car’s fastest time in the morning session on Tuesday.
WRT's co-GT programme manager Kurt Mollekens told Autosport last month that he was already “just one of the guys” and had settled in well.
Speaking ahead of Rossi’s first race weekend, Vosse said he was confident that Italian's experience and previous knowledge would mean “he will cope with the pressure” in his first full season of car racing.
Vosse said: “He is not a 17 years old kid arriving from karting or Formula 4. He has a lot of experience under his belt already.
“Yes, we should not expect too much, because he is someone who will race for a full season on four wheels for the first time in his life.
“There is a learning curve. Probably there will be some mistakes here or there. There will be some tracks that he prefers over others, like every driver.
“But the way he is handling things, the way he is preparing himself as a top sportsman will be different.”
Vosse said the team is targeting podium finishes and “the rest will come naturally”.
Though he said Rossi “knows it is a huge challenge”, the 2002 Spa 24 Hours winner believes he is “up to it”.
“He is a very curious person, he wants to know everything, he is very passionate about motorsport,” Vosse said.
“He knows motorsport very well, he knows the story of our sport. The integration into the team went very smoothly.
As I said, he is a very humble person. He gets along very well with everyone, especially his two team-mates.
“He is very humble starting into his new chapter.
“He has a lot of experience and knows how to deal with things, especially handling the pressure.
“He is someone who wants to succeed in what he is doing. He knows that it is a huge challenge, but he is up to it."
Vosse added that the team has gained “about 30,000 fans from all over the world” since Rossi’s move was confirmed.
