Why did they want to cooperate with Roland?
Roland knew their plan very well. A mage devoted to magic wouldn't be interested in matters beyond magic, which meant that the nobles, as his allies and partners, could wield his power in his place.
Though the mage might seem to be the man in charge, the actual power would be held by his allies and his partners because of his inaction.
In the meantime, the nobles would have a "shield" on the surface. While splitting up their earnings in private, they could shift the blame on their "boss" when bad things happened.
Underneath their beautiful promise was a venomous trap.
A less thoughtful man might have fallen for the trap, but Roland wouldn't lose control of himself just for some insignificant flattery.
He simply shook his head and said, "Not interested."