Sounds like a description of Clarke's 2001. Sure worked fine there, even though the novel and film are very much separate entities.
I think 2001 is probably the most overrated sci-fi movie of all time. I like quiet, intelligent sci-fi as much as the next person(bladerunner, contact, gattaca, etc.) but 2001 is self-indulgent and tedious, and I think "rendezvous" is tedious as well. I got through it but thought it was a slog.
First of all.. i've never read Rama (only got the broad story strokes through Wikipedia and other sites) so i may be wrong in what follows.
Rama doesn't strike me as good movie material without heavy changes. To put it bluntly.. huge spaceship appears in our solar system, gets noticed, a spaceship with a human crew gets dispatched, enters the ship and explores it a bit and then leaves before the space ship leaves our system. No one discerns where it came from, what its mission is or where it's going.
Now it may be fascinating on a technical level.. the scientific theories behind it, the engineering and astronomy of it but this audience is rather small. It might work as a small, character driven movie with a mystery but i guess it wouldn't break much ground with mainstream audience because there is little action and even less answers and if there's one thing todays audience expects then it's easy and understandable answers.. a neat package with a clear beginning and a clear end.
That's also why 2001 wouldn't work today in the same way it worked in the late 60s when mainstream scientific curiosity was at its highest and people were imagining the things depicted in the movie as being able to become real in a few decades (well... they could have if funding would have stayed the same later on as it was during the height of the space race).
Today SF is usually something that's from Star Wars and Star Trek.. cool special effects, cool aliens and lots of action and explosions and Rama just doesn't fit in that.
So it'll either be a smaller, "artsy" movie praised for its dialogue but nothing that would launch on thousands of movie screen.
I think 2001 also worked because, whatever its flaws, it was serious sci-fi at a time when for the most part, sci-fi shows and movies were often pretty campy.
Also, because it was 1968, people seeing it when they were high on drugs and just enjoying the trippy visual sequences helped it a lot.
you'll notice that when ST: TMP tried to follow the formula, it wasn't nearly as well-received...