The Crimson King is clearly written as Roland's enemy throughout the series. However, the man in black has shown to help Roland.
He helps Roland "draw the three" Eddy, Detta (later Susanna), and Jake via drawing three cards. Roland later comes across three doors, each of which ultimately allow Roland to grow a Ka-tet, all of which are clearly enemies of the Crimson King.
Conceivably, the man in black could have let him slowly die by infection on the beachside after the lobstrocities clipped off his fingers without any clue on how to proceed.
Either it was Ka and the Crimson King had no say-so in the matter, but then why would he send the man in black? My question is, why would the Crimson King do anything that would help his enemy?