Hi Lars,

No roads are going through Hardangervidda national park. You have a small section that has a gravel track. See here: http://www.ridewithgps.com/routes/42487147?privacy_code=98Xmv6ttqBDLpuwf

There are hiking paths all the way through the park, which connect with mountain cabins that you can stay at if open (otherwise, you’ll need a DNT member’s key). The hiking paths can be cycled in places, but you may find hike-a-bike sections. Only a good mountain bike is recommended (don’t even consider a gravel bike).
The weather on the plateau can be extreme, and you should come well-prepared for all possibilities.

http://www.ut.no/kart#9.73/60.1474/7.1365
http://www.dnt.no/