As most of the caminos follow well-established travel routes, you'll usually find a mixture of on and off-road paths. Some sections of the northern Spanish coastline are tourist hot-spots, so the towns can be very busy, although nothing like in other parts of Spain. The paved sections are usually quiet farm roads, and at some points you can choose to take the E9 hiking path, which runs right along the coast. Maybe it's just selective memory, but my recollection of the Norte is days and days of stunning scenery, farmland, mountains and beaches - 'roads' isn't the first thing that comes to mind, although I'm sure there were days when the asphalt seemed never-ending.
The thing is, over the course of a camino-month, you will experience, see, and do so much, and you will meet so many people, that the question of 'paving' could become somewhat insignificant. Although I also suppose it also depends on your motivation for doing the camino - if you're more interested in hiking, then there are many less-paved paths throughout Europe that you'd find more satisfying. If you are more interested in the pilgrimage aspect, on the other hand, then, as many other posters will probably tell you, as a novice, you should probably experience the magic of the Frances first