Speaking to Catalan daily newspaper Avui, the supremo explained that no player in the world can match the Argentine superstar, as the 25-year-old is simply a unique talent.
Skilful attacker Neymar has been likened to the three-time World Player of the Year, but Rosell says this should not be the case.
"[Neymar] has an extraordinary future, but I don't think that any player in the world can be compared to Messi. Messi is unique and unrepeatable," he said.
Rosell then went on to speak about the Spanish Supercopa second leg in Madrid on Wednesday.
"Madrid are always expected to be very competitive and it will be very difficult there," he explained. "We are two great clubs with different styles of management.
"If I start to dream then that isn't helpful. How many titles can we win? I hope for all of them. We are ready to play for this league and to fight to win it back."
The 48-year-old also answered questions on the Copa Catalunya, saying that Barcelona have not refused to play in it.
"We have not refused to play in it at any time. We would have fielded a team with a vast majority of Catalan players, and this is a good way of enhancing the image of our football club.
"We want to help Catalan football, but one must understand that we have our arguments and that no-one can tell us what team to select - it must be decided by Tito Vilanova."