excuse me,I am not sure if this is a bug or not but bulbapedia says that the move
copycat(
not to be confused with assist) does NOT activate if the last move used was roar except from gen 4.
but in pokemon showdown in gen 5 if your riolu uses roar and on the next turn uses
copycat then
copycat activates normally and you can spam +1 roar all you want.
either bulbapedia got things wrong or pokemon showdown.
I don't see this in the "not bugs" list,so I am assuming that it is pokemon showdown's fault.
https://replay.pokemonshowdown.com/gen5ou-1628591894 (just pay attention to the first 2 rounds here, I spammed roar afterwards because I didn't want the game to last too long).
BUG STATUS: CONFIRMED - MECHANICS (SERVER), you shouldn't be able to call Roar with Copycat in Gen V (DaWoblefet)