Mario is fully intangible during frames 3-6 of his up-special.
Roy is capable of performing a Ken Combo, but in order to get the sweetspot on his d-air, he needs to be at a closer range to his opponent than Jigglypuff needs to land a Rest.
And since the move is a meteor smash and not a spike, like NTSC Marth's, Roy's opponent is simply able to meteor cancel the attack anyway.
Roy will then proceed to fall under the stage and lose a stock, because he cannot recover.
poor Roy
Not only is his sweet spot at the hilt making his sword pointless, but his Dair has 8 years of recovery frames.