SAS has announced direct flights from Trondheim to Nice and Barcelona starting this summer. This complements other routes they started from Oslo to Alanya/Antalya/Faro; from Bergen to Barcelona/Malaga/Manchester/Palma/Split and from Stavanger to Barcelona/Split/Palma/Nice.
This also adds to the new flights from Norwegian between Trondheim and Sandefjord (Torp) which start in March, together with several other flights from Torp.
Besides that, it is worth keeping in mind that DAT (Danish Air Transport A/S) is also flying Trondheim – Rygge. I am not aware since how long they are operating that route, but on their website you can see that they are connecting both Trondheim, Stavanger and Bergen to Rygge. Besides that they fly in between Bodo and a few smaller airports in the north and between Oslo and smaller airports in the south. The best news is that fly search engines seem to be already covering dat, so you can search directly on you prefered flight search engine.