Roserade is a rarely seen pokemon and on Smogon, it's rated in the OU tier, which makes little since. With Choice Specs and Leaf Storm, it outclasses Salamence's Draco Meteor, despite Grass being a move of lesser coverage. It also makes an AMAZING Choice Scarf Set with HP Fire and Weather Ball in Hail or Sandstorm. the potential of 383 sp.atk and outspeeding all non-scarfers (with a scarf) is nothing to laugh at as it hits HARD!
Unfortunately, Roserade almost dies to things like Earthquake from the standard tanking Metagross. Also, without HP Fire, even Skarmory can wall Roserade. To ensure the most from Roserade, run with Sandstorm or Hail as it's a nasty surprise to get a free 100 Base Power Ice/Rock move, giving it Sleep Powder is nice with Leaf Storm, Sludge Bomb (or Weather Ball if weather is with you), and HP Fire/Ice.
I myself am considering Roserade. I just gotta get a hold of a certain set and some good IVs to work with.