There is no reason to CWE any oxycodone formulation which does not contain acetaminophen, which none of the 15/30mg "roxies" do.
There is also no reason to IV oxycodone, it has no rush, and extremely high oral BA. Not to mention a not insignificant amount of oxycodone is metabolized into oxymorphone, a much more euphoric compound; and by ingesting oxycodone in any means other than swallowing it you will be bypassing the first pass metabolism of the liver and reducing the amount of oxycodone turned into oxymorphone. Removed from the quicker onset of nasal oxycodone use, I have found that even after accounting for differences in bioavailability that oral oxycodone is a much more enjoyable experience. If onset is a primary concern, decrease the time of onset by dissolving your dose in a shot glass before ingesting.