You can raid as a resto shaman with any two professions. Blizzard also tried to balance professions so that they provided approximately equal buffs to attack power, spell power, etc. However, many players enjoy maximizing their healing, DPS and tanking abilities and one way to do so is with professions. You can find a summary of profession perks at WotLK Profession thread. The comparisons below are done with spell power and mp5, although many professions can also be used to boost crit and haste ratings.
Black Smithing > Alchemy or Enchanting or Inscription or Leatherworking or Jewelcrafting > Tailoring or Herbalism or Mining or Skinning or Engineering
Black smithing will provide the biggest boost to your stats by giving you 2 extra gem sockets. You would gain 46 spell power, 16 mp5, 21 crit rating, or 21 haste rating (assuming epic gems are introduced).
Alchemy doubles the duration of flasks and elixirs. The trinket will give a 40% bonus to potions. Alchemy also boosts the effect of flasks and elixirs, which can give you an extra 13 mp5 or 37 spell power.
Enchanting gives you an extra 38 spell power (19 spell power per ring).
Inscription gives you a shoulder enchant with an extra 37 spell power.
Jewelcrafting allows you to use 3 prismatic gems which will give you an extra 27 spell power, 9 mp5, 21 crit or 21 haste rating. It also means that by using the prismatic gems you can meet any meta gem requirement, which could be worth additional stats. The gems are not unique so you can use 3 of one kind.
Leatherworking is not as powerful as it was in the Burning Crusades. Drums are not useable at Level 80. You can gain an extra 37 spell power with a bracer enchant.
Tailoring gives a chance to restore 300 mana on spell cast.
