From a Bygone Era | Paths and consequences - recurring The Witcher 2 Choices Guide

If you choose Iorweth's path, you will not have a direct opportunity to discover the house on the cliff, and if it comes along, it will be only in certain moment. In the Roche's path you should under no circumstances sell notes to Dethmold. After locating the magician at the end of mission, you will have to make difficult decision - to kill him and obtain a good weapon, or possibility to reallocate all your talent points (in this case you will not be fighting).