Here are three methods you can try. I've used all of these. I currently use the last one (with the K2-D2 mod), but the first two methods work fine with no mods.
With no mods:
Put a control point that faces "up" when your current control point is facing "forward" and your engines are facing "backward"
Control point can be a probe core, a docking port, a command pod, or a "Grumble" seat (oriented the right way)
When you are ready to switch from "engines facing planet" to "wheels facing planet":
Cut throttle
Do "control from here" from your new control point, and orient SAS Retrograde
You can set this switch of control points to happen with an Action Group
Or this method, with no mods:
When you are ready to switch from "engines facing planet" to "wheels facing planet":
Cut throttle
Switch SAS from Retrograde to Stability Assist
Pitch nose forward to bring the wheels facing down
Let the rover land from this position
One more method, with the K2-D2 mod:
Before you begin your regular descent, open K2-D2, select Attitude Pilot, and set the following:
Set Elevation to zero degrees
Set Heading to whichever direction your rover nose will be facing when it lands wheels down
Do NOT press the K2-D2 Attitude Pilot Start button yet
Do your regular landing, engines facing planet
When you are ready to switch from "engines facing planet" to "wheels facing planet":
Cut throttle
Press the K2-D2 Attitude Pilot Start button
Poppa Wheelie's post in How can I change the orentation of prograde as it relates to my rover was marked as the answer