Among his achievements were several first ascents of routes on Trollveggen (Troll Wall), Romsdal's north facing big wall, both in winter and summer. He did the first all-free ascent of the wall in 1979 (the Rimmon Route), and the first winter ascent of the Swedish Route (1980). Most notable was his first ascent of the technically difficult Trollkjerringruta (the Troll's Wife) in winter (1982), followed by the free ascent in summer 1983. Though moderately graded by today's standards (Norw. grade 7, French grade 6c+), it is a demanding, serious climb through partly loose and poorly protected rock that up to this day has seen only two or three repeats. Doseth also increased awareness of sport climbing in Northern Europe, introducing routes in the 5.12 range (French 7b/c) in Norway and Sweden in the early 80s.