Greetings people! I'm currently GMing The Dragon's Demand, and in the last session my players managed with the kobold tribe.
Long story short: the initial way to manage with the kobold tribe was a succesful diplomatic approach. The attempt worked with the kobolds outside of the quarry and my players convinced them to parley with their chief - but while some kobolds of the tribe agreed with this, Churgri and Roaghaz were furious shouting "YOU FOOLS!" and "TRAITORS!". This ended in a battle, but some kobolds fought with the players.
The session ended with Churgri and his skeletons killed and Roaghaz defeated, but when he fell to the ground my party wouldn't kill the kobold chief - they instead take a rope and restrained him. In the next session my players plan to lead Roaghaz to Belhaim and interrogate him, and honestly I have no idea how to manage with this situation since I didn't expected they could take Roaghaz alive. What now?
This kind of development is a lot of fun for the PCs - think of it as a good way for them to make the adventure their own.
First, make a simple list of the things Roaghaz knows. It doesn't have to be exhaustive, but should hit the main beats of what the Kobolds were doing and what motivated them. This includes the fact that a being named Aeteperax is back and active (as opposed to just a name and historical information).
Then, if the PCs interrogate well/smart, they can learn pieces of this new information.
This is a good chance for the PCs to learn new information or confirm old information they've heard. Both are useful: Learning new information is a reward for their choices and confirming old information makes the adventure feel robust.
Second note that the adventure doesn't require Roaghaz to be dead. Lady Origena may be very pleased that the party brought back a Kobold for her to question once the PCs have finished their interrogation. She can still dispatch them to investigate the manor, and will consider this Aeteperax issue further based on conversations with the Kobold. The adventure can continue as written.
If the PCs want to sneak off to look for Aetepaerax, that's fine too! They'll probably die if they confront the dragon at this point, but they might get a sense it's active in the woods.