what's Roko?

The Culture has a lot of opinions of the proper way of doing things as any society does, and I'm certain that a ship doing that with its people would be considered very bad form. There are ships that decide to do things that go against the usual ethical boundaries[1], but they're outcasts. The really big ships generally have multiple minds running them, too.

Humans in the Culture are generally improved in a few ways (they don't get sick, live for 300-400 years by default etc) but still very human.

I do recall a bit about playing in different worlds in dreams though, during sleep. Ultimately, really, the average person's life in the Culture already involves doing pretty much whatever they like within reason any time, so it's not like they need to escape too much real-world suffering.

Iain M Banks himself described the relationship between humans and the ship Minds as having "a status somewhere between passengers, pets and parasites."[2]

[1] For example, https://theculture.fandom.com/wiki/Grey_Area

[2] https://theculture.adactio.com/

He explores that, but being an entertainingly twisted sort of writer he focuses more on its use for torture, with "neural laces" in Excession and virtual hells in Surface Detail.