Holy was an unstoppable force at LH. He was very fast, he could box and punch. He was also bigger than Roy and took a much better punch. The only way Roy could win is to fight the perfect fight and outbox him, but I don't think Roy could keep Holy off of him for the whole fight. Holy could also use his size and speed to box with Roy. Either way, Evander eventually gets to Roy in the late rounds.
I am definitely biased here, I could definitely see a prime RJJ hitting and running to a split decision.