1) the flare blade (Blazer is up-B) is useful because it goes slightly downward if you're boarding the edge (meaning having part of Roy's body off the edge. make sure not to fall on dreamland!). you can use it against fox/falco's side B, as seen at the Masashi vid above, but make sure to time it. remember, you want to hit every one of Roys moves with the middle of your blade for more damage, except the flare blade, which is better at the tip. plus, it's the tip that goes downward.
2) the Utilt is an extremely bad and almost useless move had it not been that you can link it in with chaingrabbing and it's, unfortunately, one of Roy's faster moves ( I suppose it's better then the jab or Ftilt). it's definitely faster then the Usmash, but I like to use the Usmash because it might spike, setting up unexpected combos. You can't juggle with it. you can, however, use SHFFLed Uairs.
3) Fox/falco's side B would hit before the dair, so I wouldn't try. as i stated earlier, you can use flare blade. if you try to edgehog, which can works since they always sweetspot the side-B, then make sure to press R or L right before they hit you. the computer thinks you're still on the edge.