Black Sludge. It provides an amazing source of recovery, and if a TrickScarf¹ Pokemon of that strategy comes into battle, it ends up depleting its own health with the Black Slime.
Also, take Earthquake over Steamroller as it does more damage and helps cover more than Steamroller.
Not only is this item great in-game, it's also great in competitive.
If the Black Sludge isn't available to you, Leftovers has the same effect. Coba or Occa berries may also work, lowering damage from a super effective flying/fire attack respectively. However, these are only one use items. Only use these if you can have a constant source of them. Expert Belt may also work, making supereffective mores do more damage. Since you have 3 different types of moves, this works as a nice alternative to Black Sludge.
Le Scarf's Glossary
¹TrickScarf = A Pokemon holding a Choice Scarf that uses Trick to make the opposing Pokemon use only one move. If the opponent doesn't switch, the Pokemon with the new item can set up hazards, use boosts, or KO a threat.