In *Kingdom Come: Deliverance 2*, missing out on side tasks can be frustrating, especially when they're tied to other quests and can't be revisited. One such task is finding Rosa's book, which is crucial not only for the quest but also for potential romantic developments with Rosa. Let's guide you through unlocking and completing the "Rosa's Book" side quest to ensure you don't miss out on this opportunity.
Before Rosa entrusts you with the task of finding her book, you'll need to complete the "Via Argentum" quest and then embark on "Taking French Leave." During "Taking French Leave," your mission is to assist the Ruthard family in dealing with Vavak, which you can do either through force or persuasion. Once resolved, you'll be directed to speak with Rosa. She'll share details about a secret passage into Maleshov, which you can use to rescue Hans. It's during this conversation that Rosa will ask you to retrieve her book from Maleshov. Make sure to ask her specifically about the book and promise to bring it back to her, officially starting the "Rosa's Book" side quest.
Upon entering Maleshov, head to the largest tower where Hans is held at the top. Use the stairs on the side of the building to enter. Once inside, sneak past the guards by hiding in the kitchen until they leave the tower.
After the cutscene, continue with "Taking French Leave." Although Hans opts not to use the passageway, you can progress towards romancing him by selecting the dialogue option with a heart symbol, provided you chose the heart option in Trosky as well. Sneak to the north side stables, knocking out and hiding guards as necessary. Clear a path, signal Hans, and ensure his safe passage to the stables.
Open the gate, and you'll enter another cutscene, concluding the quest. Once it's over, return to Kuttenberg City and stop by Ruthard Palace to deliver Rosa's book, completing the side quest in *Kingdom Come: Deliverance 2*.