Derived from iLol, a joke used mainly by Microsoft employees to mock the way that Apple adds an 'i' to the start of things to make it theirs.
Add multiple 'i's for emphasis, e.g. Roiiiiiiiiiiiiifl!
Jon: No, wait. Oh Yea! iLol
Andrew: And that video she posted,
Jon: Yeah I saw that, Roifl!