Below are three easy suggestions for helping your rogue get raiding ready in Cataclysm. Do not expect to hold on to your Icecrown Citadel non-heroic and heroic level epics. You will start finding upgrades as early as Uldum around level 83 while leveling.
All Cataclysm factions are easily grindable through the use of Faction Tabards. These scraps of cloth are purchasable from Quartermasters for the various factions at the Friendly reputation level. There is a small selection of 333 gear available at Revered and 346/359 gear available at Exalted from various factions. Some other reputation necessities for rogues include the shoulder enchant from Therazane reputation in Deepholm and the helm enchant from Ramahken in Uldum. Rep reward gear is also very useful for hitting the 329 item level score that is required for your character to enter heroic instances.
2. Justice Points and Heroic Dungeons
All of those JP you have banked from the end of Wrath can give you a head start on your new PvE outfit. If you can pick up one or two pieces of gear, it can save you massive amounts of grinding time. The Thrash Blade 1.4 speed off-hand dagger is a great starter for Assassination rogues.
3. Conquest Points
One win on a 2v2 Arena team currently = ~268 Conquest Points
5 X 268 = 1340
The conquest point cap per week for a new team/lower rating is currently set at ~1343 Conquest points. So 3 weeks of arena will currently net you a main hand and off hand weapon of greater than 420 dps.
As always, you can also check out the rogue forums over at Elitist Jerks (www.elitistjerks.com) for the latest in theorycrafting such as stat weights, rotations, gemming, and general practice.
Happy New Year!