Its a good start, however you are going alot for poison, dont forget that steel also is super effective versus fairy and takes little damage in return. How long does Roserade stay alive, when I did this fight, I went with Toxic Spikes and Venoshock alongside my Aggron and was able to make it through.
Im surprised that Blaziken is still in your team, mine got bodied during this fight. Other then that, anything like the recommended Milotic/anything that can take a hit will be good in this fight. Be aware that clearing the mist in this fight does not make the field neutral, but then becomes a fairy tale field, which boosts steel and fairy type moves, so that can be used to your advantage, but also helps Adrienn