Here's what I use:
Roserade (F) @ Choice Specs
Trait: Natural Cure
EVs: 252 SAtk / 252 Spd / 4 HP
Timid Nature (+Spd, -Atk)
- Energy Ball
- Sludge Bomb / Shadow Ball
- Hidden Power [Fire] / Hidden Power [Rock]
Extrasensory takes care of Fighting types. With maxed Speed and Timid Nature, Roserade should be able to take them out no problem, especially with Specs.
Energy Ball is for STAB.
Sludge Bomb is for STAB. Go with Shadow Ball if you want coverage against Psychic types.
HP Fire is for steel types, since all of your moves are ineffective against them. I use HP Fire because of common threats such as Ferrothorn, Forretress, and Scizor. HP Rock covers basically all your weaknesses except Psychic.
If something gives you a status, just switch out. Natural Cure will take care of your problem.