If you are having trouble with stealth rocks, bring a spinner, kill their stealth lead, never worry about rocks again. If Volcarona did not have roost expect it never to be used on a team without a spinner, 50% off even if you're a sweeper sets you up to be hit by anything. PLUS you need a turn to set up, and there's not many situations where someone would switch out when they could possibly put Volcarona into priority range.
In a similar vein, if you take out the opponents auto you can set up your weather whenever you want. Neither Ninetales or Charizard is going to stand up against a Hydro Pump in rain, but maybe if you invest thoroughly in Sp. Def you might be able to survive one from a bulky Politoed set, because you know water is neutral against Charizard Y. Of course you could obviously predict the move and switch into Venusaur and then just Leech Seed or Giga Drain. In a weather team, you should expect not to win the weather war every time, so you can always throw in things which work in normal conditions like a Scizor, which gets OHKO'd by fire moves in normal weather or a Dugtrio to trap Ttar.
If you're worried about rocks, take care of them, simple as that. And when you're versing a normal team, then you get free Fire Blasts off Charizard. Ninetales is either run physically defensively for Will-o-Wisp or Specially Offensively to weaken priority targets of a team. Charizard looking at the stats, can probably pull both of these roles better.
