What does the entity speaking to Roland mean that he Darkles and Tincs.
I never got this impression of Roland during the entire series.
Isn't this the "coloring of dreams"?

Does he have some power over his reality.

For example Pere Calahan tells of his conversation with the man in black. How he was offended at the suggestion that the gunslinger might in fact be above KA.
Now I was thinking that the whole point of the quest was some kind of process for Gan/God to regain its sanity. Every time he completes his quest God regains more of his sanity.
The crimson King represents the part of God that allows evil as part of all freewill. While Roland is the part of God that must stop itself from descending into complete chaos and madness. The multiverse becoming more frail over time because God has for whatever reason listened to the darker aspect of its nature.