In West Limgrave
Your first meeting with Roderika will take place in the Stormhill Shack located in West Limgrave. To get here from the Gatefront Ruins Site of Grace, head in a northwesterly direction and then follow the path upward until you reach an open field. When a pack of wolves lands on the ground below you, you’ll know you’re getting close to the correct location. After activating the Site of Grace in the Stormhill Shack, proceed inside the building to locate her. She will be sitting on the ground there.
Conversation with her should continue until she hands you the Ashes of the Spirit Jellyfish, at which point she will ask you to travel to Stormveil Castle. It is not enough to simply visit the castle; you must also recover an important relic known as the Chrysalids’ Memento in order for the quest to proceed. From the Site of Grace atop the Rampart Tower, which is located on the western side of the castle, head in the direction of the east. Proceed along the ramparts until you arrive at the room containing the Grafted Scion foe.
After passing through the door on the south side of the room, you will arrive in a courtyard with two canines and a pile of dead bodies. On top of the pile, you will find the Chysalids’ Memento. Take this with you, and report back to Roderika. Simply reloading the area will reveal that she has moved on to the next location.
At the Roundtable Hold
Have a conversation with Roderika at the Roundtable Hold, and then have a conversation with Smithing Master Hewg. Continue to switch between the two characters, picking the novel dialogue option that appears each time, until Hewg finally gives in and agrees to be Roderika’s mentor, albeit reluctantly. Roderika will now have the opportunity to train as an apprentice in Spirit Tuning once this is done (mechanics-wise, this means she is now a vendor that will level up your Spirit Ashes).
When you reload the area, you’ll notice that she has moved away from the fireplace in the main room and is instead seated on the floor across from Master Hewg. This can be seen when you reload the area. She will remain in this location for the duration of the rest of the game. It is important to keep in mind that it is in your best interest to monitor both her and Hewg’s dialogue options as you progress through the game because they will occasionally offer lore or conversation topics.