If you are looking for some quality souvenirs, I recommend Heimen Husfliden at Glasmagasinet. Husfliden is the 'official' shop for all traditional wear, so anyone making a bunad (the Norwegian national costume) buys fabrics and courses through Husfliden. So, you know you will get quality stuff here. Buy the famous knitted Marius jumper, the thick Røros woolen blankets, or some yarn to knit your own souvenir?