Only big things to worry about here are delays in inbound flight (if you have a European passport). If you are on time this should work, if you are getting a delay you are soon to find your self in a stressful situation.
All over - Oslo is efficient - my record from leaving the airporttrain to being at a domestic gate is 2:30mins in the morning rush (Fasttrack and HBO that is). I am on average through OSL every second week both domestic and international at various days and times. Personally I would not have such a tight connection on separate tickets (unless it is my only option) as there are few alternatives if things go wrong. And I also guess 2 hrs are below what most travel insurances will cover?
Also - if you see "Boarding" on the monitors for QR, do not panic. They are normally putting that up way ahead of boardingtime so would probably show "Boarding" when your MAN-flight is landing.