Roserade first appeared as Budew in Dawn Of A New Era! performing a Sunny Day, which stopped Ash and Dawn from fighting. Nando appeared with his harp and told the group that the Budew was his. He battled Dawn with Budew while Dawn used her Piplup, despite Piplup having a type disadvantage. As Piplup was about to use Peck on the Bud Pokémon, Budew dodged and covered itself up with smoke. Piplup then used Bubble Beam to make the smoke disappear but was proven ineffective against Budew. Budew began to use Solar Beam and as Piplup was about to use Peck for a second time, Budew's Solar Beam made contact and took out Piplup.
Later, Budew battled Team Rocket as Carnivine was about to attack Piplup and took Carnivine out in one hit. The next morning, Budew battled Ash's Pikachu and used some healing moves to avoid losing energy. It evolved into Roselia during the middle of their battle. However, despite the evolution, it lost to Pikachu as he dodged Roselia's Solar Beam.
In A Secret Sphere of Influence!, Roselia was at the Eterna Historical Museum. Prior to the events of the episode, it had a Gym battle with Gardenia's Turtwig and won. Nando was taken in along with Roselia for some questioning. Around the end of the episode, Nando was proven innocent.
In Dawn's Early Night!, it teamed up with Kricketune in the Battle Stage of the Hearthome City Pokémon Contest, which was held under the Double Performance format. They battled Jessie's Seviper and Dustox and won.
During Nando's long absence, Roselia evolved into Roserade. In Coming Full-Festival Circle!, it was sent out along with Nando's other Grass-type Pokémon, Sunflora, during the Battle Stage of the Sinnoh Grand Festival. It was able to get Nando past the top 8.
In League Unleashed!, Nando sent Roserade out as his first Pokémon during his match against Ash in the Lily of the Valley Conference. It went up against Ash's Staraptor. During the battle, Roserade's Sweet Scent caused Staraptor to become temporarily immobile, which the Bouquet Pokémon followed up with Magical Leaf which scored a direct hit on Staraptor. Roserade then tried to finish off Staraptor with Solar Beam. Just when things were about to get bad for Ash, Staraptor got up and dodged at the last second. Staraptor finished Roserade off using its wild-card technique, Brave Bird.
Roserade appears to be one of Nando's signature Pokémon, along with his Kricketune. It has shown to be in sync with its Trainer, listening closely to his commands. Although it does not know any sound-based moves like most of its teammates, it is a calm and poised Pokémon, which fits Nando's personality.
Since Nando collects both Ribbons and Badges, Roserade has been used in both standard battling and Contest Battles. Having experience from and being skilled at these two fields makes it a versatile Pokémon overall. It has also proved successful when battling with a partner in two-on-two battles, as shown during the Hearthome Contest, which followed the Double Performance format. During the event, Roserade battled alongside Kricketune to earn Nando the coveted Hearthome Ribbon, his second Ribbon overall.