Flagg can't read Roland's mind

The dark man on the green throne continued to smile, unperturbed. “Roland?” he asked. “What about you?” Slowly, he raised the drawstring bag. It looked dusty and old. It hung from the wizard’s fist like a teardrop, and now the thing in its pouch began to pulse with pink light. “Cry off, and they need never see what’s inside this—they need never see the last scene of that sad long-ago play. Cry off. Turn from the Tower and go your way.”
“No,” Roland said. He began to smile, and as his smile broadened, that of the man sitting on the throne began to falter. “You can enchant my guns, those of this world, I reckon,” he said.
“Roland, I don’t know what you’re thinking of, laddie, but I warn you not to—”
“Not to cross Oz the Great? Oz the Powerful? But I think I will, Marten . . . or Maerlyn . . . or whoever you call yourself now . . .”
“Flagg, actually,” the man on the throne said. “And we’ve met before.” He smiled. Instead of broadening his face, as smiles usually did, it contracted Flagg’s features into a narrow and spiteful grimace. “In the wreck of Gilead. You and your surviving pals—that laughing donkey Cuthbert Allgood made one of your party, I remember, and DeCurry, the fellow with the birthmark, made another—were on your way west, to seek the Tower. Or, in the parlance of Jake’s world, you were off to see the Wizard. I know you saw me, but I doubt you knew until now that I saw you, as well.”
-Wizard & Glass