Roche's given reasons for not riding for Visentini change all the time. As you say, he mentions that Visentini wasn't going to ride the Tour. He also mentions that he was stronger than Visentini (although Visentini won one of the TTs - Roche won the other), which is probably the most important one. Counter to that, he was an irishman riding an italian race for an italian team, whose nominated leader (an italian) had won the race the year before. He then attacked his own team leader, who was in pink, and then stayed on the front whilst his entire team tried to chase him down.
I know, totally ace. Love it if Froome pulled it this year
I know, totally ace. Love it if Froome pulled it this year