I really liked how your set looked RaikouLover but I'm not one for copying so I made a similar yet differnet set.
Roserade @ Black Sludge
Ability: Natural Cure
Nature: Calm
EVs: 252 HP / 252 SpD / 4 Sp Atk
*Energy Ball
*Rest/ Leech Seed
*Leech Seed/ Sludge Bomb/ Spikes
*Toxic Spikes/ Spikes
I opted for 0 Spd EV's to hopefully gain maximum recovery from Rest and with Max Hp/ SpDef EV's Roserade can take her fair share of hits. Leech Seed will help force switches, Sludge Bomb can hit Celebi hard, and Spikes works pretty nicely as well.
Sleep powder is necessary for roserade to lay down spikes and hurt it's opponent. Leech seed will never work on a frail pokemon like roserade unless your opponent is asleep or retarded. On top of that, the EV spread is thoughtless.
Rest is a good move, and I've had some success with it, but with no other forms of damage besides a grass move, you're not going to be killing anything anytime soon, so why waste that 125 special attack? The same walls will wall her every time. Skarmory, metagross, jirachi, celebi... Take off leech seed at least and replace it with an attack. HP fire preferably, since it hits all those pokemon who wall her for SE besides heatran. With your current set, weavile... WEAVILE could switch in safely and break your face. Weavile should never be able to switch in safely.
What's left over after tweaking your set? Calm nature. Calm nature only works if your opponent expects sleep powder and switches to a sponge, but without substitute, she can't expect to ever pull off leech seed. Even bulky roserade works better in timid. Lets also pull the special defense out of EV's and throw that all into speed. The HP is fine because if you know about evening defenses, you want your HP to be slightly higher than your SPDef.
But seriously, if you want to try this on roserade, I have to ask... why not use it on pokemon who can actually TAKE hits? The only thing roserade offers here is the combination of leech seed and toxic spikes, but she can't use them together very effectively at all, so it's not worth it. You sacrificed crucial speed for arbitrary numbers of special defence and hitpoints, without any thought into just WHAT you made outspeed roserade. Her decent speed was the only thing stopping her from being dead weight in OU, allowing you to hit an opponent with sleep, set up spikes OR toxic spikes and switch out, only to come back later and sleep something else or hit with a powerful attack.
I have to ask, have you actually used roserade in OU before?
Sorry to be so blunt, but there is just a serious lack of thought in this set.
P.S. Leftovers over black sludge. If your opponent will take the sludge from you, what's stopping them from giving it to another member on your team?