Level 50 Statistics (see level 5, 50, 100)
Roselia is one of few Pokemon in NU that has access to Spikes, which she can set up reliably thanks to her Grass-, Water-, and Electric-type resistances and good special bulk with Eviolite. Her typing and relatively high Special Attack also allow her to stop various Pokemon in NU, such as Ludicolo, Alomomola, and Seismitoad. Unfortunately, Roselia's Defense is rather lackluster even with Eviolite, leaving her vulnerable to common physical attacks, such as those from Golurk and Scolipede. She also faces competition as a Spiker from Scolipede and Garbodor, as the former has a better offensive presence and the latter has better physical bulk to tank Fighting- and Bug-type attacks.
This set takes advantage of Roselia's access to Spikes and solid special bulk which allows her to switch into most special attacks with relative ease. Roselia can also use her immunity to Toxic to grant her free switches and start setting up Spikes. Rest restores all of Roselia's HP, increasing her longevity at the cost of having to switch out so that Natural Cure can wake her up. Synthesis can be used instead, as it lets Roselia stay in longer and set up more layers of Spikes. Giga Drain is Roselia's primary STAB attack, hitting common Pokemon such as Golem and Samurott for super effective damage. Sludge Bomb is useful for hitting the many Pokemon that resist Giga Drain, such as Charizard, Tangela, and Serperior, and gives Roselia a way to hit Pokemon with Sap Sipper.
Team Options & Additional Comments >>>
With an offensive set, Roselia can serve as a bulky offensive pivot and status absorber for more offensive and balanced teams. Roselia can come in, take a hit, strike back with strong STABs coming off of base 100 Special Attack, and use Sleep Powder to disrupt the opposing team. The ability to absorb Toxic Spikes along with Poison STAB really separate Roselia from other bulky offensive pivots such as Tangela. Without Spikes on this set, Roselia is able to use Sleep Powder to cripple would-be checks that would normally have nothing to fear. Sludge Bomb is Roselia's most powerful STAB move, and it has really good neutral coverage and a handy chance to poison the foe. Giga Drain, Roselia's other STAB, covers the Ground- and Rock-types that resist Sludge Bomb, and it also lets Roselia take on bulky Water-types such as Seismitoad and Alomomola that can be problematic for offensive teams. Synthesis allows Roselia to remain healthy throughout the match, and it can be used to heal up against the Pokemon that are put to sleep by Sleep Powder.
Team Options & Additional Comments >>>
Roselia has a great support movepool with moves such as Aromatherapy, Stun Spore, Cotton Spore, and Toxic. She also has access to Toxic Spikes, which could be used instead of Sludge Bomb on some teams. Extrasensory is an option to hit Poison-types such as Garbodor and Scolipede harder. Roselia also has access to Sleep Powder, but because it's illegal with Spikes, it rarely sees use. As Roselia's typing is more suited to taking physical attacks, one could choose to run an EV spread of 248 HP / 252 Def / 8 SpD with a bold nature to capitalize on this. Keep in mind that Natural Cure is really the only ability you should be using on Roselia, as Poison Point is too unreliable and Leaf Guard is basically an inferior Natural Cure that needs sun up in order to work. Finally, Roselia could also utilize her relatively high Special Attack on an offensive set with Leaf Storm or Giga Drain alongside Sludge Bomb, allowing her to hit opponents hard and get more chances to set up Spikes, but Leaf Storm is illegal with Spikes and Roselia faces competition as an offensive Spiker from Scolipede.
Checks and Counters
Despite Roselia's impressive bulk with Eviolite, nearly any physical attacker can take her down. Sawk, Golurk, and Scolipede can all at least 2HKO Roselia. On top of that, not even Roselia's special bulk can protect her from the Psychic-, Fire-, and Ice-types throughout NU; Pokemon such as Jynx, Gardevoir, and Charizard all make short work of her with their super effective STAB moves. Steel-types can also switch into Roselia with few problems. Klang is one of the best options as it can simply set up while all Roselia can do is use Spikes or switch out. Poison-types are in the same boat, resisting both of Roselia's STABs and even absorbing any Toxic Spikes Roselia might have set up. Muk, Skuntank, and Golbat are good choices, as Muk can OHKO with Ice Punch, while Skuntank can damage Roselia on the way out with Pursuit, taking away about half her health. Golbat, while unable to absorb Toxic Spikes, takes almost nothing from Roselia's attacks and can OHKO her with Brave Bird. Finally, while they might give her a free turn to set up, both Knock Off and Trick remove Roselia's precious Eviolite, rendering Roselia far less useful.