Guardiola was appointed Barca coach in 2008 by then president Joan Laporta, who was succeeded by Rosell in 2010.
Two years later Guardiola quit the Catalan club to take a sabbatical in New York, before agreeing to take over as coach of Bayern in January this year.
Speaking at a press conference in Lake Garda, Italy, where Bayern are conducting their pre-season training, Guardiola was asked a question about a story that appeared in the Brazilian press earlier this week.
It claimed that Santos vice-president Odlio Rodrigues said Guardiola had encouraged Neymar to sign for Bayern instead of Barcelona, telling the player's father that Vilanova would be unable to manage having both the Brazilian and Lionel Messi in the same team.
Guardiola denied the story, saying: "I don't know the vice-president of Santos but probably his intermediaries have got this very wrong, because the information they have given him is false.
"I would never make any comments like those he said I made."
The 42-year-old claimed he had spoken to Neymar three years ago, at Rosell's request, to convince him to sign for Barcelona, and met him at the Ballon d'Or awards in January.
Guardiola also admitted speaking to the player's father in New York when he became the Bayern coach "to see what his situation was".
He said: "In that meeting and in the two conversations we had before that I must have told him 20 times how well he would do at Barcelona, and in none of those three meetings did the name Tito Vilanova come up.
"It's not necessary for me to say if he [Vilanova] is a capable coach or not, he was my assistant for five years and what he did last year speaks for itself, because he led the club to their greatest season in their history.
"What's more, the best players can always play together and those two [Neymar and Messi] are capable of playing together for many years."
Guardiola then moved on to Rosell, saying: "I told them [the president and his directors] I was going 6,000km away and asked them to leave me in peace, but they haven't kept their word.
"I did my time [at Barcelona] then decided to leave.
"I want them to get on with the job and I wish them all the success in the world, because their success will also be mine, I don't need to say what I feel for this club."
Guardiola's biggest bone of contention with the board was the suggestion that appeared in the press that he had not made enough effort to see Vilanova when he was diagnosed with cancer.
He said: "Too many things have happened that have crossed the line.
"I will never forget that they used Tito's illness to cause me damage, because it's a lie that I never saw him in New York.
"I saw him once, and the reason I didn't see him more often was because it wasn't possible, and that wasn't my fault.
"To say that I don't wish the best of someone who was my colleague for so many years is very bad taste, and I didn't expect that."
Barcelona will face Bayern on 24 July in a pre-season friendly at the Allianz Arena and Guardiola said he will be cordial when he sees Rosell again, but will not be able to forget what had happened.
"I did the best I could at Barcelona," he said.
"The staff and coaches have nothing to worry about. I left and have nothing to complain about, all I asked was to be left in peace. I went off to learn English and I ended up trying to learn German.
"That was all I focused on. I just ask the board to go their own way and leave me alone and stop using me and my friends to hurt me."