hell no. Roy gets absolutely destroyed by jiggs. Also, the up-b thing only kills puff on yoshi's story (unless they don't DI on FD).
It'll kill on stadium too, even if they DI.
But yeah, point still stands. Reverse upB doesn't have much range, and if you whiff its a free rest. Only two stages you can depend on the reverse upB to kill, and the only real time you can use it is out of shield...and no puffs will be landing right in front of your shield.
Roy's two redeeming features, his down tilt and fsmash, are pretty much useless against jiggs. She's never going to be on the ground, and all of her priority tears through fsmash. Grab game is zilch since shes floaty, the only real thing thats possible is down throw -> fsmash at super low percents, and thats only if they DI wrong.
The only thing roy can really do in the match up is overB tap -> jab over and over, and then hope jiggs does something dumb at kill percents.