Level up Rockruff to level 25 during the day to evolve into Lycanroc Midday Form
Level up Rockruff to level 25 during the night to evolve into Lycanroc Midnight Form
Level up Rockruff to level 25 at dusk in Pokémon Ultra Sun, Ultra Moon, Sword, Shield, Scarlet, or Violet to evolve into Lycanroc Dusk Form
Use a Rockruff with the Own Tempo ability and level it up to level 25 in Pokémon Ultra Sun or Ultra Moon to evolve into Lycanroc Dusk Form