After reading up on Roiland and his past ventures. I'd be hesitant to say it was his writing that made the show. I'll have to catch up on R&M to really know. But I really don't feel like that dude is packing literary nukes in his pocket. Harmon was the one originally approached for R&M, Roiland has like Acceptable.tv as one of his only writing gigs besides R&M. I think the bulk of the talent came from elsewhere he is mostly a voice actor.

Harmon is the much better writer. Rowlands writing has been less involved for years now. The worst episodes are Roilands input.

With Harmon as sole writer the show is bound to hit a stride.

I heard Roland hasn't written for Rick and Morty for many seasons now.

https://movieweb.com/rick-and-morty-co-creator-justin-roiland-has-not-been-in-the-writers-room-for-years/