Hi, There are several routes on the site that go from Oslo to Gol. It’s a very common cycling route.
I don’t know what you mean by ‘drive your routes from the back’.

Here is another option that I hope helps. Go to the National Cycle Route overview map and you will see a yellow and orange line showing you the national cycling route from Oslo to Gol. Download these gps files and modify them using which ever program you prefer (Komoot, ridewithgps, strava, etc, to fit your requirements.

http://www.cyclenorway.com/routes/national-cycle-routes/overview/

A video explaining how to download and modify the gpx files can be found here: http://www.youtube.com/watch?v=hk3LkZ1SArU

From Gol you can follow the orange line to Geilo. Then from Geilo you can follow the green and blue lines down to Rauland.

Everything you need to plan your route is on this website. I’m unsure if I can help you further on this matter. I wish you a safe trip.