A much better idea would be to train a new Diglett/Dugtrio/Trapinch/Whatever to level 49, and try it instead, or simply use Mean Look and Taunt, which would prevent Raikou from using Roar, or if you're feeling confident/suicidal, you could try using Encore instead.
If you can in some way manage to get a Pokémon with both Mean Look and Baton Pass, you could Baton Pass the Mean Look to an Octillery and have the Octillery take it out.
Or you could simply try using a Wobbuffet and hope you get your counter right...