I'd say keep Giga Drain and Extrasensory, since both of them are useful if you want your Roserade to live longer and deal some decent damage.
Now, depending on your team, I would say get rid of Toxic Spikes if anything, unless your team utilizes Toxic in some way. They aren't too useful anymore, since Toxic is not always the thing to use (I choose Thunder Wave or Will-o-Wisp for the stat drops), and quite a few Pokemon are immune to it (i.e. Steel types, Flying types, and Levitaters). Besides, you're using an offensive set, so why not go all out? Petal Dance is one of the best Grass type moves there are, after all~