In *Kingdom Come: Deliverance 2*, some side tasks are easy to miss, and failing to complete them can be frustrating since you can't return to them later. One such task is finding Rosa's book, which is crucial if you're aiming to romance her. Here's a detailed guide on how to unlock and complete the "Rosa's Book" side quest.
To unlock this side quest, you must first complete the "Via Argentum" quest and then start "Taking French Leave." During "Taking French Leave," you'll help the Ruthard family deal with Vavak, either through force or persuasion. After resolving this, you'll be directed to speak with Rosa. She'll inform you about a secret passage into Maleshov that you can use to rescue Hans. During your conversation, Rosa will ask you to retrieve a book for her while you're in Maleshov. Make sure to ask her about the specific book and promise to bring it back to her, which officially starts the "Rosa's Book" quest.
Upon entering Maleshov, head to the largest tower where Hans is located at the top. Use the stairs on the side of the building to reach the entrance. Once inside, you'll find another set of stairs and a small kitchen nearby. Hide in the kitchen until the guards upstairs leave the tower.
Following the cutscene, continue with "Taking French Leave." Although Hans doesn't want to use the passageway, you can work towards romancing him by choosing the dialogue option with a heart, provided you made the same choice in Trosky. Sneak to the stables on the north side of Maleshov, knocking out and hiding guards as needed. Clear a path, signal Hans, and ensure he reaches the stables safely.
Open the gate to trigger another cutscene, which will conclude the quest. After the cutscene, return to Kuttenberg City and stop by Ruthard Palace to give Rosa her book, completing the "Rosa's Book" side quest in *Kingdom Come: Deliverance 2*.