In RGT you can upload GPS files as 'Magic Roads'. (premium version). It will then create a virtual road for you to ride and track the route/gradient of the GPS file.
One thing you need is good GPS data, as I've experienced cycling on 0% gradient then in an instant it's 25% and the trainer locks up!
To avoid this you need to smooth the GPS file to take out any bad data This can be done with gpx smoother and gpx magic.