MotoGP veteran Valentino Rossi will not be retiring from the sport in the wake of his friend Marco Simoncelli's death at a crash in Sepang.Honda's Simoncell died after a horror collision during the Malaysian MotoGP when he was struck by bikes ridden by Rossi and Colin Edwards.Rossi, a winner of nine World titles across various classes, was so distraught after the accident that he opted to issue statements on Twitter.He tweeted: "Sic (Simoncelli) for me was like a youngest brother. So strong on the track and so sweet in normal life. I will miss him a lot."TRIBUTES POUR INDavide Brivio, Rossi’s manager at former team Yamaha, denied widespread rumours that the Ducati rider was too upset to carry on racing. "Many are asking about Vale stopping races. This is absolutely not true and I'm sorry that I even have to explain it."Tributes have continued to pour in for Simoncelli from the motorsport community with his death coming only a week after British IndyCar driver Dan Wheldon was killed in a 15-car crash in Las Vegas.MotoGP bosses have started an investigation into Simoncelli's collision but have said it was too soon to comment on the fact his helmet came off, though video of the collision clearly shows that it did.