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Forces the target out, dragging out another random non-fainted ally. Fails if the opponent's team does not contain any inactive Pokemon. Fails if the target used Ingrain previously or has the ability Suction Cups. Pokemon protected by Magic Coat or the ability Magic Bounce are unaffected and instead use this move themselves. This move has a priority of -6. Pokemon with the ability Soundproof are immune. This move cannot be blocked by Substitute.
Forcing the opponent to switch has several advantages. Firstly, the opponent has no control over what is switched in, which makes it likely that the opponent will be forced to switch again. Secondly, the switch-in is forced to take entry hazard damage, which is especially advantageous for defensive teams that rely on it as one of their primary damaging methods. Lastly, it can save the team from an opposing setup sweeper that has gone out of control, even if it has a Substitute up. Since Roar has negative priority, it is commonly seen on slow, bulky Pokemon, such as Giratina in Ubers, Heatran in OU, and Blastoise in UU.
Many defensive Pokemon have the luxury of choosing between Roar and Dragon Tail. The advantage of Roar is that it works even if the opponent has a Substitute up, whereas Dragon Tail may merely break the Substitute. This can especially be a problem in match-ups such as a Bold or Calm Blastoise vs Kingdra in UU, where Blastoise's Dragon Tail may not even break Kingdra's Substitute. On the other hand, Taunt disables Roar, and Magic Coat and Magic Bounce reflect it. These factors cause many Pokemon to choose Dragon Tail over Roar.
Circle Throw is a Fighting-type equivalent that also causes damage.
Dragon Tail is a Dragon-type equivalent that also causes damage.
Whirlwind is another Normal-type equivalent that bypasses the Soundproof ability.