Roswaal's Mansion is one of Roswaal's Mansions and was first seen in "The Happy Roswaal Mansion Family". It is later revealed to be his reserve second mansion and his real mansion being another one which is located near Costuul.
In the climax of Arc 4, the mansion burned to the ground after Otto Suwen and Petra Leyte poured oil all over the kitchen floor and set it on fire, in order to get rid of a fearsome Demon Beast. Following the destruction of the mansion, Roswaal and the other inhabitants of the mansion temporarily moved to Miload Mansion, located not far from Roswaal's old mansion.
The Mansion is a giant white house with five watchtowers with the fifth one being the center one, a giant garden and a black roof. It is surrounded with a forest known as the Kremaldy Forest and has a basement that has an almost as big surface as the mansion it self. At the end of Arc 4, the mansion burned down and Roswaal, along with the members of the Emilia camp have moved to his main mansion.
- Entry: Upon entering it, it's noted that the mansion retains great elegance. There are two pillars with a pair of lamps each. In addition to having high class designs, there are lights near each door, as well as vases with flowers. On the road there are two routes to the sides, right and left, and stairs to go up to the next floor.
- Kitchen: In that place the servants of Roswaal prepare breakfast, lunch and dinner. It is full of plates, pots, jars, rollers, knives and other things that can be used to prepare food. In case you need to buy more food, they go to a market and transport the products by putting them in a barrel.
- Bathroom: The bathroom can be used a sauna and has few marble pillars in it. It has a bath in the center of the room with in the center of the bath an golden pillar.
- Washbasin: It is used for personal hygiene, it contains the same white washbasin, a toilet with a brown lid and a mirror decorated with a golden frame.
- Guest's Room: It is the place where the head invites their visitors to talk. It is observed that it has three green furniture and a small rectangular table in the center, to its surroundings there are also windows with light green curtains. It is noted that there is a fireplace and above a picture showing a drawing.
- Dining Room: In the dining room, all the people in the mansion gather to eat. In this place there is a large table covered with a white tablecloth, on each side there are several chairs, and regardless of the time, lights are placed on the table. The wall is green and has certain white spaces. Behind the table there is a figure in a painting, possibly a relative of the Roswaal family.
- Forbidden Library: The Forbidden Library was a massive library built by the Witch of Greed with the purpose of housing her vast knowledge converted into Magical Books. Some time before the Witch's demise, she installed Beatrice as the Library's keeper, until the arrival of That Person. The Forbidden Library was mentioned to be the most knowledgeable place in Lugnica. Appearance-wise, it's a huge two-story space with a spiral stair in the centre of the room. The second floor consists of a large balcony which is filled to the brim with bookshelves. Despite it being accessible through any of the Roswaal's Manour's doors, the Library itself isn't inherently part of the mansion, as it exists in a separate dimension that can be accessed through the teleportation mechanic called Door Crossing. During the fight for the Roswaal's Mansion in Arc 4's climax, Subaru, Otto and Petra managed to set the mansion aflame, which resulted in the entire mansion and the Forbidden Library burning to the ground. Furthermore, before her demise, Echidna made a mechanism that would erase the knowledge from every book in the library, should Beatrice abandon her role as the Forbidden Library's librarian. This was done so people wouldn't kill Beatrice in order to get their hands on the infinite knowledge hidden in the Forbidden Library.
- Garden: The garden is located on the outskirts of the mansion, it has several characteristics, such as that it is full of grass, besides there are also several paths where you can walk. On the sides you can see small fields full of flowers, you can also see some large trees and other small trees, as well as bushes. There are also places to rest.
The mansion was directed by Roswaal A Mathers , later on several rooms were made, like a library where most of the knowledge of Echidna was saved, who created Beatrice to keep them safe. With the passage of time, the mansion came to belong to the margrave, Roswaal L Mathers, he hired Frederica Baumann as his maid, then he brought Ram and Rem, later he also took Emilia under his roof as his Book said so, she would only stay studying for the Royal Selection, to become the future queen. In order to keep his body in shape, Roswaal took the prana from Ram's horn every night. A couple of months before Emilia lost her insignia, Frederica stopped working at the mansion.
When Emilia brought Subaru as guest because he helped her with her lost insignia, he opted to work as a butler, helping the maids with the activities. Roswaal suspected Subaru, thinking that he was a spy, however, he went to attend some business. Sometimes Subaru visited Beatrice to ask her some things, until she discovered a shaman dog capable of making curses, so Subaru with the help of the maids managed to defeat him, at the last instant Roswaal reappeared, helping them to defeat the Wolgarms.
After a visit from Felix, and after having held a conference in the capital, Subaru stayed at the Karsten mansion. Rem decided to accompany him. Roswaal once again attended some affairs at the Sanctuary. Beatrice stayed longer in the library, Ram had to do double work due to the absence of her sister, so Emilia was completely alone. A few days later, Subaru returned with some merchants in order to evacuate all the people from the territory to the capital and the other half in sacred land, all to face the Witch Cult. Due to her contract, Beatrice remained in the mansion, on the other hand Ram called Frederica to take care of things in her absence.
Instantly there were a series of consequences, since Rem was erased from existence. When Subaru returned accompanied by Emilia and Otto , Frederica took care of them, she also hired Petra Leyte, who accompanied her in her work. A few days later, Subaru, Otto Suwen and Garfiel Tinsel returned from the Sanctuary to the mansion, where they confronted Elsa, as well as a few Demon Beasts controlled by Meili, unleashing a chaotic battle that little by little ruined the place even more. With Meili captured, the group left, not before Subaru made a new contract with Beatrice to leave the mansion, which ended up collapsing on top of Elsa.
- Roswaal A Mathers (first generation) (former)
- Roswaal J Mathers (9th generation) (former)
- Roswaal K Mathers (former generation) (former)
- Roswaal L Mathers (current generation) (current)
- Roswaal A Mathers (former)
- Julia Mathers (former)
- Karl Mathers (former)
- Roswaal L Mathers (former)
- Beatrice (former)
- Frederica Baumann (former)
- Ram (former)
- Rem (former)
- Emilia (former)
- Puck (former)
- Natsuki Subaru (former)
- Petra Leyte (former)
- Untill three months before the start of story, the mansion had many servants but according to Frederica, Roswaal sent them–including her–on leave in order to prepare for the troubles the Royal Selection would bring.