First - level up your team a bit.
Get them to about Lvl. 42 - Lvl. 45
Sneasel vs. Empoleon
Take it down with any Steel STAB
Piloswine vs. Roserade
Roserade's high SpA stat and Spe against Plioswine's meh SpDef and poor Spe could work. Use a move like Energy Ball.
Abomasnow vs. Staraptor
Knock it out using Aerial Ace / Wing Attack / Fly, whichever Flying STAB you have.
Empoleon vs. Froslass
Any Steel STAB you have would work
Or you could just use Empoleon against everything, just watch out for Piloswine. Using Roserade and Staraptor may be a bit risky, but their good Spe and high SpA / Atk could OHKO / 2HKO them.
Hope I helped!