If Roglic had covid when he started the Giro (luckily without symptoms in that case), he shouldn't be worried about it now and is prime for winning the Giro. Must be hist luckiest GT up until now. Biggest competitor got sick and he is immune when the fight for the marbles start.
Roglic being a superspreader would give cases in his team first instead of the rest of the peleton. I think it is clear from Evenepoels case what happens if the GC rider has covid. (3 remaining). So think that idea can be abandoned, burried, stabbed and killed.
Of course we don't know if Roglic had covid before or during the Giro. So he might still not be immune. Lets hope for the Giro Roglic/Thomas/Hart are all immune or completely symptomless to the point of not testing positive.