It's not Roy's Speed which has Diminished a lot, it's his Reflexes

Sure he speed may be a tad diminished but it's mostly his reflexes which have worn down the most and are why he is getting hit Reflexes are the first thing to go with age. It's why all the Tennis serve and volleyers retired earlier than their baseliner counterparts. In terms of his physical gifts, Roy was in his prime 10-12 years ago.