Yeah, check out my guide here
I don't cover roles in there as you'll see MorganBB who took over for me mention in there they are having trouble with it, but he also may have some good advice.
My .02 but know I don't use OKTA any longer so I can only offer theory more than specific help since I have nothing to look at - Roles are a pain in the **bleep** when trying to push from OKTA into Khoros. Instead, I would highly recommend using custom profile attributes to trigger the role assignments. Create something like "KhorosPartnerTrigger" as a custom attribute in Khoros, and map it with OKTA. Using OKTA, Push the value of "true" via the saml assertion into that attribute, which would then just trigger the Partner level rank(s) to add the "Partner" role when that attribute is set to true (Same thing my guide says about creating a badge, you would just create a rank instead)