Why Ron/Oliver?
None of you will probably believe me if I say; "It's all in the canon, baby!", so I might as well go with; "They look good together."
But then you'll probably mistake me for a horrible pervert, so let's not do that, mmkay?
I do admit; This is one of those weird ships no one really ships, or if they do, they don't really discuss it much, or support various other ships. It's not really anyone's "main ship", if you know what I'm saying.
Is it MY main ship? Fuck no. But then again, what I ship depends on my mood. I do always ship Ron/Oliver, though. For some reason, they've just stuck on.
I could bring out the books and point at pages and go: "SEE! Ron/Oliver-evidence!", but honestly, who bothers? The fact is that they don't really talk to each other in the canon ...at all. They're hardly at the same sequences and they hardly acknowledge each other's existence, but all this happens for a very good reason;
THE SEXUAL TENSION IS TOO MUCH FOR THEM TO BEAR!
This is why they don't communicate much. It would just drive them both bonkers with mad lust. Yup. I rule.