King wrote the screenplay for Rose Red. It was based on a project he
and Steven Spielberg tried to put together many years earlier, but they
couldn't agree on the story's focus. So King did it himself.

The company that owns ABC also owns the publisher Hyperion. Someone
came up with the idea of doing a media tie-in book, but King didn't
have the time to write it so he suggested his buddy Ridley Pearson, who
spent time on the Rose Red set. His presence there let him inject into
the diaries things like a funny allusion to King's cameo in the
miniseries.

No, Kingdom Hospital was based on the Danish miniseries "Riget"
(Kingdom), directed by Lars von Trier. King rented the miniseries when
he was in Colorado filming The Shining and felt inspired to acquire the
American rights to the story. The rights were tied up with another
company at the time, so he exchanged the film rights to "Secret Window,
Secret Garden" so he could do the adaptation.

The Journals were another media tie-in idea. King had read some of Rick
Dooling's novels (one of his examples in On Writing comes from a
Dooling novel). Knowing Rick's medical background, he asked him to be a
medical consultant on Kingdom Hospital. That relationship progressed to
the point where Rick became a co-writer on several episodes. HE was the
natural choice as the person to write the tie-in.