Sorry this isn't OD material, no HR value here and we aren't here to help you the most high possible, we're all about safer drug abuse.
I would recommend you go with 20mg roxicodone because IR medication is easier to deal with in general, you can titrate your dose a lot more reliably than the ER medication, plus the OPs are notoriously inferior to older forms of oxycodone such as roxicodone.